OptiFine's developer is sort of known for not wanting to open up his project and accept outside help. A lot of people are turned off by that but personally I think it is whatever.

The biggest thing is that it is a mess of horribly unoptimized code, hobbled together over more than a decade. In some newer versions, OptiFine can actually perform worse than vanilla. Their rendering changes also cause many issues with other mods, and since it is closed source, developers can't fix them.

Fabric or NeoForge running a handful of mods is vastly superior. It has been a bit but I would recommend looking at Fabulously Optimized as plug-and-play alternative | https://github.com/Fabulously-Optimized/fabulously-optimized