While it is possible to build some pretty elaborate stuff in Minecraft using redstone, it typically requires a ton of space. In addition the game has poor support for sending power up or down.
For example, if you want a building with multiple floors and each room has a lever or button that turns on an overhead light in the room, it requires that the space between the ceiling and the floor above be 3 blocks thick (one layer for the ceiling, one layer of air that the redstone goes in, and then one layer for the floor of the room above). This is a tremendous waste of building space. And if you are trying to create something that incorporates an if|then|else structure, it's going to basically require building a room just to handle that.
The solution is obvious. Allow all solid, non-transparent blocks to have two versions: for wired vs. non-wired. You make a block wired by putting it in the crafting table with redstone. What comes out looks the same (or perhaps has a small 2x2 pixel redstone bump on each surface to denote that it has changed) but is named something like "oak wood planks (r)" with the r meaning it has redstone embedded in it. A block that is wired, if receiving power from any one direction, outputs power in all 6 directions. So a chain of these mixed in with the regular blocks in your floor/ceiling allows redstone power to be sent along that line. And the floor/ceiling only needs to be 1 block thick instead of 3. And you can send power up and down without having to use some wonky work-around.
I am not proposing to replace the redstone system we have already with this. I don't want to break existing stuff people have built. I just think they should add this in addition to what we have now to allow for redstone that is cleaner, more compact, and more easily hidden.