Don't get me wrong, I'm still a grumpy asshole, but I try harder to be decent. I try to be the dad that the kid deserves, and that includes setting an example by being better than I used to be.
It's some powerful shit, when you let yourself feel it.
It's a commitment. If you are not willing to have your life completely changed then yeah, you better not do it.
It's not a path for selfish people. There is not a lot of "me time", as a parent.
IDK that I'd be so quick to refer to people who don't have kids as selfish.... Certainly there are selfish people that shouldn't have kids for that reason, but not all people who are willingly childless, are selfish.