I don't realy understand what this means but heres what the crash log said

Caused by: org.spongepowered.asm.mixin.injection.throwables.InjectionError: Critical injection failure: Callback method taxfreelevels$removeAnvilLimit(Z)Z in taxfreelevels-common-neoforge.mixins.json:RemoveAnvilLimitMixin from mod taxfreelevels failed injection check, (0/1) succeeded. Scanned 0 target(s). No refMap loaded.

Minecraft version 1.21.5 neoforge verson 21.5.4 mod version 1.4.9-neoforge-1.21.5

Wow, this broke fast!
Worked on 21.5.0 just fine, let's see what changed...

Fixed in 1.4.10!

(It looks like NeoForge applied some vanilla fix or something like that. The new Mixin shouldn't break any time soon now. Famous last words.)