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.
Why would they do that? They specifically made bedrock edition so that the game could be more cross platform, which has worked extremely well for them financially.
Java edition has never been playable on anything other than Windows, Mac, and Linux, porting an SDL version onto any of those is extremely easy.
Getting everyone on one platform is a much better model for Microsoft than trying to resell you a copy on each device.
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