Focusing mainly on this, since I piped up only for the fact part and not the opinion (which is yours and completely fine to have :3 )
Really depends on context. When done to livestock (why would you kill off healthy animals that fit standard instead of letting them grow to be eaten or sell them off?) or pet mammals, it's the removal of weaker and non-standard genes from the breeding pool. In livestock, that usually means death (why waste resources on animals that will not give max production?). In pet mammals, if they can survive, it usually means spay/neuter asap and rehome to a pet-only environment. Some breeders will kill the nonstandard pups, but that is becoming a lot rare due to the popularity of the spay/neuter cull instead. In animals that are hunted, culling is population control for things such as deer, wolf, and feral pig populations. Again, it might be different in the context of reptiles, but outside of that culling is not just people killing off healthy animals just to create a pretend limited resource.Definition of CULL
transitive verb
1
: to select from a group : choose <culled the best passages from the poet's work>
2
: to reduce or control the size of (as a herd) by removal (as by hunting) of especially weaker animals; also : to hunt or kill (animals) as a means of population control
— cull·er noun