FPS are constantly low

When I join a world, doesn't matter how big it is, I only have 5 FPS or so, but only in Minecraft 20w22a, not in the full version. If I turn the Render Distance to 2 Chunks and Smooth Lighting off, nothing happens. I can turn everything to the unlaggiest option, but nothing happens.

And again in version 1.16.2 Pre-Release 2...