Two topics… the problem with death, and the largest strengths and weaknesses at different game stages. They are split into subtopics, feel free to read just one, but really almost all are necessary.
DEATH IN A GAME
Necessary to have consequences for death that doesn't ruin fun but makes you want to stay alive
->punishment for death vs reward for staying alive
-If you die that sucks and being dead actually crosses your mind and you wish you were alive
-If you live you don't think about the benefit of being alive, and the fact that you don’t want to be dead doesn't cross your mind (usually, most exceptions being near death)
Thus, there is no reason to add additional punishment for death, and you should be rewarded for staying alive (to remind you not to take for granted that you are alive). Players are immortal, the need to survive has to be different than it is in real life, not just a burden to grind back items or start a new. See A below for setup based on immortality. Skip to B for a mode like hardcore that deals with setups where players are not immortal.
-So, firstly, keep inventory should be enabled. No more punishment should be added to dying.
-exp loss might be reasonable, adds complexity and nobody cares too much about losing it
-perk for living x time or killing/doing x tasks without death. Could be something as abstract as an achievement, trophy, or player banner. Could be more useful like a skillpoint, a new craftable item, a new ability, or even a new dimension!
-needs to be joined with changes to difficulty so game doesn't become increasingly easy if you are thriving and never die
B.) Keep in mind that this is an adventure game that people grow attached to. Sure, a few players want a YOLO experience, but most of us just like the thrill of needing to survive at all costs. This is where normal gameplay is typically at. We grind all the time to avoid dying, because as mentioned before, it sucks to die. Problem is, we grind so much that we can't die, and avoid dangerous EXCITING moments as a result. Of course, we risk dying in certain situations (don't have much to lose, easy to recover losses, and boredom [note this last one is a result of not enough challenge])
-Again, keep inventory should be enabled
-not YOLO, but instead, YOL x times, or each life you lose an ability. Lives are better than abilities because if you lose an ability after dying you are just more likely to die, whereas each life is separate with no negs on future lives.
-You can gain new lives or add abilities by doing risky things like killing a creeper and a skele within x time. lives are better than abilities for similar reasons to the opposite affect.
-You can trade lives for abilities, autonomy brings curiosity and allows players to make the most of a bad moment.
-failure to be risky results in a death by boredom (forces players to not rind away to stay alive)
How to keep the game as difficult as it is late-early stage (i.e. no bed and no light with minimal armor and tools at night while hunting for food on a low hunger bar), interesting as it is mid stage, and as eventful as it is late stage
INTERESTING (let's get to the buzz kill first)
--It's a huge problem late game. There are two ways of amending this, making an extremely filling and long midgame that almost no one will ever complete, or add a lot of features for what people call endgame. Here's the thing about this game. It's an adventure. An adventure game is exactly that, the adventure. Open world makes it feel autonomous, but at the end of the day, once the adventure is over, interest will die. This is not fixable, BUT some people can be satisfied with minigames. These are really whole new games, and we can't break it to ourselves because we have grown too attached to our adventure, so we want a part of it to live on in these new games that are keeping us interested. So if you add skills and attributes to a character, they can keep that uniqueness when they enter these new "mini" games. Can be stuff like pvp, npc town building and wars, creative competitions, endless waves of enemies, etc. Just important that the player that was born from the original survival game is unique and capable in these "end, mini" games.
--Interest is also a problem early game because the startup is always the same. Punch a tree, table, pick, dig for stone, upgrade tools, get some food, make/find a bed or go underground once you have coal for lighting. Then things start to get more complex, you can start a farm, go exploring for treasures, or mine and loot caves like no tomorrow. This can get even more complex in modpacks. Once you have found your interests, you are enjoying the game the most. This is where midgame gets it right. There is an abundance of ways you can be affected and steer towards certain skills/features, and there is an abundance of things to do. It almost always feels new because you aren't forced to do it in a certain order, and the same path isn't always guaranteed to be the best and most likely taken for your style of gameplay. Solution to the early game repetition? Force a random (or manual for those who seek less challenge) different startup. Realism mods hint at how this is possible by adding steps that you need to do in the beginning that are interesting and complex, but they are still usually the same every start. To expand on those ideas, there needs to be different ways to start. Usually if a player spawns in a mountain, an ocean, a desert, a prairie, or a ice land, the first thing they do is leave the biome in search of one with trees to start the same pattern. What if they couldn't reasonably leave that biome? Ship crashed and burned up in a new world with a toxin that your tech is auto removing, but you can't enter those areas until it has been cleared, a lack of energy to travel because of early malnutrition post apocalypse or something, or genetically adapted to thrive in one environment but need tech to survive in others. Any of these reasons or possibly some others would require the player to make do with what the biome has. There would obviously need to be adjustments to biomes to allow players to start off successfully with what is in each. Each spawn could be joined with a item that the player brought in preparation. scuba kit/net/spear for ocean, grappling hook and pickaxe for mountains, axe for forests, shovel, bucket and hoe for prairies, food and water for a desert, skates leather and wool for ice. Punching wood and finding a few sheep to kill can't be the only way to start.
--What can you add to make the sweet spot of mid game longer? More well executed features. Could be stuff like magic, engineering, exploration, any type of field complexity. Needs to be evolvable for each game stage to keep it interesting AND attainable. Not grindy. This is something a decent amount of mods do very well, but there is usually two ends of the spectrum hit well, with very few getting a good balance. The spectrum being smooth, well thought out, limited additions to insane amounts of content that is very unorganized.
CHALLENGING [something almost all, if not all, mods and game modes struggle to get right] -difficulty should increase if you have survived x amount of time or done x things without dying x time(s) or been above x satiety or x hp for x time or tasks
-difficulty doesn't need to, and shouldn't just increase in mob complexity or strength. Other attributes should be increased in difficulty based on what the player is or is not struggling with (e.g. if food hasn't been a problem, make the overabundant sources harder to get, harder to make, or not as nutritious)
+Could start to experience more fall damage, random crippling, malnutrition, temperature influence, obesity (too easy food access), dementia (useful for modpacks that have a large amount of crafting recipes and a searchable field), slowness, confusion, and other debuffs.
+NOTE: All debuffs should be amendable. E.g. you don't want to cripple an endgame player with slowness to such extreme that they can't return to normal or optimal speed with proper potion or other resource use, and you don't want it to be annoying either, nobody wants to waste an inventory spot carrying around speed buffs just to counter a debuff.
+Debuffs should be curable for players who want to remove it. It should be a very challenging process that is different every time and requires well thought out plans. Therefore, players who are really set on removing a debuff will see it as a challenge worth completing, while others will just counter the debuff with short remedies.
+Difficulty jump should be optional, a server can force or leave it to the player.
=Rewards can also be implemented for upping if players seem too incentivized to stay at a lower difficulty (and maybe grind until they are bored).
-have different bosses at the end of each step (or difficulty if combining with above mentioned change for challenge)
there should be several possible bosses for each stage to add variety and prevent grinding to prepare for a particular boss. Forcing bosses should be an option, if a server is made to force players to progress it can be enabled, but if want players to have the choice to take it at their own speed, bosses can be manually generated just like difficulty can manually be increased.
-quests add purpose, but they need to have a story, not a goal to get a certain item or do/kill xyz
-Seasons can add variety
-creative short term effects that can have long term consequences (e.g. temporary random crafting recipe change, portals that lead to new dimensions or transport players to unexpected places, food sources that become infected, blocks that give off affects, mobs switching roles).
THAT’S A WRAP! Please comment what you think and/or would change/add/remove, and even if you don't like my ideas, upvote this thread if you think these topics do need to be addressed (whether it be in vanilla, or in some extensive mods/complete modpack). That way, a dev might see this and make a commitment to it or your ideas below.