Minecraft is horribly under-optimized, but unfortunately a lot of the deeply architectural things might be impossible to touch without breaking something for the more technical players. (Check out Docm77 or TangoTek, they're really pushing the game to the absolute limits.)

If you don't mind clientside mods, there are a few dedicated to optimizations, including rendering: sodium, lithium, phosphor, optifine. I'd recommend PrismLauncher and Fabric for managing/loading the mods.