I understand you say that you didn't mean for it to be judgey but I think your true feelings showed through the text.
You say youre in your 20s - I expect what's probably happened is that your immediate group of friends have all started to have babies. And because you (and/or your partner) have decided to wait til you have a mortgage first - and because current house prices - you know it's going to be a good few years before you can have babies so you're trying to placate your own feelings (jealousy + broodiness) by telling yourself that it's irresponsible to have kids before a mortgage and those doing it are wrong and you're right for waiting.
I say this because I have friends who have kids and friends who are waiting like yourself and the latter have expressed similar views to yourself whilst also clearly being jealous of the fact others have babies and they don't yet (and have admitted this to me in private). In my friend's case her partner had insisted no babies before mortgage and she felt she had no choice but to stick with that and so belittled others who had babies already and were renting to make herself feel better.
As many PP have said already - you can have all that and lose it all after kids come along. Or start without it and get it later (having kids doesn't make that impossible btw). Or even as others have said - they left it til after they felt financially ready only to experience troubles with conceiving as they left it too late.
My H and I don't have a mortgage. However we have 2 kids. Both of us bring in enough income to where we can afford childcare for both (I work part time). We don't claim any benefits except child benefit. If we couldn't afford the child care, I'd give up work. But for now both of us are in jobs with good career progression options which means in the future we shall be able to get a good mortgage between us.
We figured we could wait to have children til after we had a mortgage - but with that comes risk of potential fertility issues (it took us a while to fall pregnant actually so glad we started when we did!), increased chance of the child having a disability or at the very least a more difficult pregnancy and labour. Btw the latter can have life long consequences if it goes really wrong. Physical damage sustained during childbirth - like all injuries - have a greater chance of healing well if you're younger than if you're older. Your body's ability to heal could make the difference between life long poo incontinence for example.
Or we could have them now, live frugally whilst the kids are little and don't know any different (babies don't care they're in charity shop clothes) and by the time they are in school we'd be financially better off due to career progression so their memories won't be of them being denied things other kids have. We will be able to buy them nice things.
People have (and continue to do so in very poor countries) raised lots of children on very little money. And the British standard of poor is much better than what poor is in other countries. I'm not advocating that we raise children in a poor environment but I do believe that having children needn't be as expensive as you claim it is. And definitely having a mortgage in place before having children is a preference and not a necessity.
It's good you feel comfortable with your choice, but you getting into a flap about other people's choices indicates you aren't fully settled and content with your choice. Maybe take some time to think again to ensure you're fully content with your decision to wait.