This exact same guide is also available on the Empire Minecraft forums: [PSA/Guide] Why you shouldn't use OptiFine [1.16+] | Empire Minecraft
OptiFine was one of the best mods, if not the best mod, in Minecraft versions 1.6 through 1.15. It offers some performance benefits, shaders, dynamic lights, zoom, and about a million other things in one neat package.
However, OptiFine since 1.16 does not meet its former glory.
Some of the major issues of OptiFine include:
- It is monolithic. You don’t have precise control over what features you do and don’t get.
- It has awful support on Fabric/Quilt. A large portion of Fabric/Quilt mods are incompatible with OptiFine. Its support on Fabric/Quilt even isolated by itself is spotty.
- It updates slowly. When I first wrote this, OptiFine was not yet updated to 1.17, while almost all of the mods I provide as alternatives were updated to 1.17. Even for the one that hadn’t yet updated, someone had ported it themselves within under a day.
- It is not Free Software, and it is closed source. Closed source applications have far less opportunity for growth and collaboration than Free & open source projects do. If someone wants a feature or bug fix, with Free software, they can just fix it in the code themselves, if they so desired. To quote the Free Software Foundation:
However, by far the most striking thing about OptiFine is the fact that better alternatives exist. That’s what this serves as: a migration guide from OptiFine to alternative free & open source mods.
First, let’s go over some of the main use cases of OptiFine, and their replacements.
I use OptiFine for the performance benefits.
If you use OptiFine for the performance benefits, you should use Sodium, Lithium, Starlight, FerriteCore, EntityCulling, and LazyDFU. These mods give more FPS than OptiFine in almost every use case (and even just Sodium alone does absolute wonders). See this video for a demonstration.
You might also want to follow my guide to maximizing performance on Quilt, which can be found here.
I use OptiFine for the shaders.
If you use OptiFine for the shaders, you should use Iris. Iris has great support, and depends upon Sodium for optimal performance. Metrics that I’ve seen on Iris’s Discord show quadrupling of frames going from OptiFine to Iris+Sodium.
The thing to note here is that Iris is still in development. This means there are some shaders that might not work fully. However, all hope is not lost. As of 2022-04-29, they’ve got PBR in beta testing!
I use OptiFine for the other aesthetic changes.
A few aesthetic mods work with Sodium & Iris right out of the box, like Fabric Capes and LambDynamicLights. However, some mods require a compatibility layer called Indium, due to technicalities with the APIs that they use.
If you put Indium on top of Sodium, you can also get other mods to work, including Continuity and LambdaBetterGrass.
I use OptiFine because it’s easy to install.
Fair enough, I suppose. However, if you play Minecraft with any level of frequency, you probably should still give these mods a shot. Long-term benefit is better than short-term gain.
My use case isn’t listed here.
A long list of OptiFine alternatives can be found here. If that still doesn’t cover it, feel free to contact me directly. I have quite a bit of experience with going from OptiFine to Sodium & friends because I once used OptiFine too. I learned of these alternatives, and therefore, I wanted to share my methods. 
I haven’t spent dozens of hours on research and work for only myself to reap the benefits of shaders with a good framerate on a 2013 laptop. ;)
I’m having trouble installing these mods!
The Quilt Discord is an awesome place to get support! This isn’t an ‘official’ guide, but nonetheless, I’m sure we’d still be able to help you out over there!
Conclusion
Wait, you actually read through this? I didn’t think people actually read through my various modding rants. Have some nice Iris shaders screenshots taken by me as a present. I think all of these use Sildur’s Medium, but they might use Lite or Extreme-VL, I honestly don’t remember.
Save travels in the NO-ptiFine realm!