That's a shame, he has responded on the Minecraft Forge forums though, along with some other devs, to questions about forge and optifine compatibility. The good news is they are compatible theoretically, but you can't easily get Forge to load Optfine first (or something like that, I'm not an expert,) so actually it's on the Forge devs to make it work. You used to be able to install Optifine as an internal mod on a Forge profile via Magic Launcher, but now it doesn't work with 1.13+ Forge, so that's a problem. I'm going to try this method suggested for 1.12 on the minecraft wiki https://minecraft.gamepedia.com/Mods/Installing_OptiForge/Manual_Install/Modify_Existing and I'll report back if it works.
Unfortunately sp614x hasn't mentioned anything about Magic Launcher getting updated yet, but if more people suggest it as a solution for the Optifine+Forge problem, then maybe he will look into getting it working for Forge 1.13+
Edit: apparently according to the Forge devs, it's on the Optifine devs to make it work. Uh oh. https://www.reddit.com/r/Minecraft/comments/acc07m/optifine_and_forge_for_1132/
Edit 2: Nw guys, as of April sp614x has said they have a solution they're working on https://github.com/sp614x/optifine/issues/2148