the data simply disagrees. 100 years ago things were much, much worse, yet people had more kids. people can cope all they want but their complaints don't align with reality and all measurements which indicate that more developed countries have fewer kids, not more. though i know that admitting one is selfish isn't something most want to do, so i definitely get why people rationalize it by other reasons.
The problem with the "richer countries have fewer kids" correlation is that it implies causation, but I think it's more sensible to say it the other way: "having fewer kids makes you richer" (at least temporarily, before the demographic collapse makes you poor again, but that will likely not be your problem).
Share your data and what's "worse". Again, we've polled people and they're literally telling us it's too expensive.
The cost of raising a child is enormous. It's dramatically higher than it was 30 years ago, and astronomically more than a century ago. I've known multiple households with dual 6 figure incomes where one quit their job to be a stay at home parent because the cost of childcare was comparable to the reduction in income.
The cost in time is just as bad - no more "go outside and don't come back until dinner", now if you let your kids walk down the street to school/the park your neighbors will call CPS on you, so you have to pay attention all the time.
Rent/mortgages are way up. The cost of food is way up. The cost of education is way up.