Their sample was fine, but them subsampling it to present clickbait misinformation is not. Here [1] for instance are some interesting broad picture datums. General planned fertility hasn't changed much at all over the years, but rather people are simply failing to achieve their goals. The percent of people with the intent to remain childless (100% of the sample in the studies you linked to) remains relatively negligible, rarely more than ~15% per age bucket, and generally much lower. So those views are quite unrepresentative and fringe.
The relationship between economics and fertility is widely accepted, but surveys have been hijacked by clickbait. Going the other direction with studies is also difficult because it's well established and taken as a given, rather than studied. But this [2] seems to be some older foundational study on the topic. ctrl+f for "opportunity cost." Essentially the more people earn, the more they lose out by having children, which is seen as a major deterrent to having children. In other words, they don't see themselves as having enough money to afford what they would lose by having children, so prioritize earning more, to buy more things, over having children.
The relationship between economics and fertility is widely accepted, but surveys have been hijacked by clickbait. Going the other direction with studies is also difficult because it's well established and taken as a given, rather than studied. But this [2] seems to be some older foundational study on the topic. ctrl+f for "opportunity cost." Essentially the more people earn, the more they lose out by having children, which is seen as a major deterrent to having children. In other words, they don't see themselves as having enough money to afford what they would lose by having children, so prioritize earning more, to buy more things, over having children.
[1] - https://onlinelibrary.wiley.com/doi/10.1111/padr.12535
[2] - https://pmc.ncbi.nlm.nih.gov/articles/PMC3576563/