Can confirm this is still an issue in version 1.21.2.02
Something to note; this issue not only occurs in brand new worlds, but also effects both Modded and un-modded Worlds.
Can confirm this is still an issue in version 1.21.2.02
@Ian plant could you share what you did that fixed your issue?
Further update, I enabled client-side-chunk-generation-enabled on the server that I help run, with render distance set at 20, and this actually caused a lot more issues than when it was disabled.
Not only was the nether laggy, but the overworld starting lagging more, with chunks taking anywhere up to 30 seconds to load in.
After disabling the client-side-chunk-generation-enabled, the world goes back to only lagging when players go to the nether.