What if, birth rates are a much more complex topic that can't be reducted just to one cause or the other but a cumulation of multiple factors.
Personally from where I'm standing (EU urbanite), I see the falling birthrates seem to be mostly caused by unaffordable housing in the big cities where most young people live, which seems to plague most of the developed west, as that's where all the jobs the young generations are taking, but there's no affordable space to raise a family in.
Sure, you can move out of big cities to the countryside with affordable land, but you'll either have to give up your white collar job and social circles you worked so hard for, or spend hours per day commuting (no, fully remote work isn't an option for most employees unfortunately). So middle class couples are struck between a rock and hard place where they're constantly waiting for the winds to turn in their favor till their biological clocks run out.
To me it seems that mass urbanization, as in the move from rural to urban, is a huge factor in killing birthrates across the world, not just the west, but also in places like China who in their rural poverty days had too many people that they had to cap the max number of children by law and now when a lot of it is urbanized and developed, they have the exact opposite problem.