It’s an oversimplification…but not a big one.
It's a massive oversimplification that seems to whitewash China's policies.
Every country that undergoes industrialisation and urbanisation has a big drop in birth rates. Same in capitalist and socialist countries, there's no essential difference in how it plays out (the tempo is different from case to case for many reasons, but the trend is the same). But China additionally made the rates plummet through govt intervention.
So you stressed and praised the part that wasn't truly crucial for the outcome (socialism), but ignored the part (one child policy) that drastically contributed to the outcome and that can't be presented as nice or intuitively desirable (regardless of whether it objectively was or wasn't a good decision). That's not simplification but selectiveness.
(Yes, it is true that many lemmings who live outside China just project their own "China sucks" logic onto the Chinese, and their approach is wrong, I agree with you on that count.)

Hmm...