Why is it ethical to consider health of the line in animal breeding but unethical in humans?

To be clear, I believe every human who wants to have children should be able to and no one should should be prevented. I am asking this in good faith.

Now that we've established that, why is it? If someone wants to breed their pet, there are strict guidelines about how to do so in an ethical way that include: knowing the health of the line, not breeding too young/too often, not breeding animals with known aggression or health issues, committing to quality vet care, vetting buyers, and being willing to take the animal back from the buyer at any point in the animal's life if the buyer needs to give them up. These are all good things, and anything less than that is considered unethical "backyard breeding."

However, if we tried to impose those same "rules" on human reproduction, it would immediately be labeled eugenics. Someone has a known genetic defect they will likely pass on to offspring? You can't tell someone not to have kids. Someone has had 5 kids in 6 years and their body needs a break? You can't tell them not to have kid number 6. Someone is 50 and wants fertility treatments? You cant tell them they're too old. Someone has clear anger management problems? You can't tell them not to have kids.

We don't apply the same qualifiers to human reproduction as animal breeding. Why? Is it solely because humans are conscious of and can generally prevent pregnancy if they want? Is it because animals are just biologically driven to reproduce and can't reason for themselves if it's responsible and so we make the choice for them? And if that's the reasoning for animals, and we impose those rules because it's what's best for them and their offspring, why are those same guidelines considered highly unethical instead of responsible for humans?

Please don't come at me saying I'm a proponent of eugenics. I'm not. (See first paragraph.) I'm just trying to understand why we think about it differently.