What if someone is not waiting on anything and just doesn't want to have kids out of any number of reasons? It's alright if you have regrets, but I don't see it as selfish if you never intended to have kids in the first place.
Also noteworthy is that I don't project an opinion of selfishness on others; it's what I feel of myself. I can say also, now having a lot of friends that also waited for whatever reason, it's not uncommon in this cohort. It's also very common that people wait then run into fertility issues and the feeling hits harder for them. We've known a ton of people that struggle hard with that, more-so if having kids was already on your must-do list and you just delayed it too long.
So to answer your question more directly, I don't think the person you described is selfish. They may however realize they were if they ever decided to actually have kids and perhaps have some regret do to that.
As long as you participate actively in society by working, you are doing your part and are not being selfish.
Not having children isn't even a new concept. People have done it since time immemorial. What if they had multiple children and then lost them all to the statistically high child mortality rates? Were they being selfish by not furthering their lineage due to external circumstances?
These seem like very clear exceptions and reasons. Take it as a general sentiment, I'm not trying to footnote everything I write online to consider every possible circumstance any human could conceivably encounter. I think you should have known these are clearly not selfish acts. Biologically infertile being selfish? Come on dude.