i've had an issue of low and stuttering FPS in minecraft for years now at first i thought it was because i had Ryzen 5 2600 which isn't exactly singlecore beast which minecraft likes but then i started seeing in forums that it's because Minecraft uses OpenGL which AMD GPUs don't like.. i didn't believe this at first because how can a blocky pixelated game run like SH*T on a (at first RX 590) RX 5700XT i was searching and searching and found nothing some fixes were working but only for like 5FPS gain which is nothing really.. so i asked my friend if i can borrow his old GTX 960 and i was blown away it got nearly TWICE the amount of FPS (and MUCH smoother) than with my RX 5700XT
i did 2 tests one with Vanilla Minecraft (no mods) and one with mods both on version 1.16.1 (latest as of writing)
the ones where i am standing on a RED block are done in vanilla and the ones where i am standing on a GREEN block are done on modded
both have same settings and in both i rendered all the chunks by looking around first and then capturing the FPS
you can clearly see that an old mini single-fan GTX 960 is beating a new RX 5700XT (Sapphire Pulse)
which is very disappointing as i had many issues with the card, most of them got fixed but the feeling of a bad purchase never goes away and with this i don't even think it can be fixed because it's like 6 years since this started happening on AMD cards
It has to do with AMD software recognizing OpenGL as 2D app. So you are running Minecraft, a 3D application and the GPU is kicking it’s feet back in state0 at its base clock (probably 300-400 MHz). This has been an issue for years but no fix from AMD - of course.