My own experience in life makes it reek a lot like mental health issues in those who are antinatalists.

I mean, is that not a good enough reason not to have kids?

Assertions I'd like to make, in no specific order:

Yes, my retirement might not even happen because of falling birthrates.
We live in a world of finite resources and an imperfect method of distributing them.
It's only going to get worse, especially with climate change.
If we don't have a population contraction voluntarily now, eventually we're going to have one involuntarily later, as people turn to force.
Wars over constrained resources are an end in and of themselves. It doesn't even matter if you gain control of other resources; if you win, you get more resources to buy your people a little more time. If you lose, you got rid of a lot of people who need and want things.

These problems are all solvable. These problems are also not plausibly going to be solved, as those who have will do their level best to turn away from those who have not. We have literal centuries of evidence neatly showcasing just how selfish our systems are, and how resilient to change they are.

You can absolutely have as many kids as you want. I personally think it's myopic, as you're forcing someone else to deal with these problems and you didn't even give them an option - and by the time they're old enough to understand the magnitude of the problem, they're in too deep to get out. It just screams of selfishness and duplicity to me. But, I mean, I'm still friends with omnivores - hell, I'm one myself - being selfish and inconsistent is kinda fundamentally what humans are, so it's not like my shit doesn't stink too.

Edit: I should also note that the one reason I allow myself to eat animal products is because I've said "well, I'm not having kids, so I'm just a temporary problem, not an ongoing one"