When mods such as EMI or REI are displaying a lot of animated items in one page, the frame rate of the game immediately tanks.
It helped majorly when Exordium used to cap all UI frame rate playing with mods such as Simply Sword, with Mythic Metals, back in 1.19.2,

Now on 1.20.1, I have Immediately Fast, Sodium, and ModernFix with fast item rendering enabled, but none of them have been able to alleviate the issue.

Yea old versions had that, but mods like REI just render too badly, so this wasn't worth it. Also, it's in the inventory, there is no real point to having more than 60 fps there.