We have 3 cats (indoors unless supervised by one of the humans, to protect birds and other wildlife), 2 who showed up on our doorstep, ill and hungry, and one from our local rescue. We are also (hopefully) temporarily caring for a relative’s 3 cats. I’ve switched the lot to poultry only food, no beef or fish, in the hopes of less environmental impact.
While I believe keeping cats indoor is the responsible thing to do, in many places habitat destruction and use of pesticides has a much more negative, and much bigger, impact on birds and wildlife than cats could ever have.
I think that breeding licenses should be very limited, and that spay/neuter should be mandatory for all pets that are old enough.
As for kids, we already know we need to reduce the population, not add to it. Otherwise there won’t be much quality of life for anyone. But many people are too selfish to care, they decide they want 2 or 3 or more kids and to hell with the eventual consequences.