Cave anglers spawn in high qualities (Q200+++) from any cave level and can be cheesed from really early on.
With the possibility of refreshing the spawn area every ~20 minutes or so, you can get insane quality stuff in high quantities early on with little effort.
I had access to a big river on L1 with Q250~Q300 cave anglers from day 1 this world, giving me high quality bone/leather/hides/strings and a decent curio from the start. Only being capped by my survival.
By checking the river every +- 30 minutes I got 2~3 cave anglers an hour on average.
Reduce either the maximum quality of cave anglers, reduce their spawn rate or cap their max quality based on cave level. Cave anglers are OP!