Most startups fail, and most startups are run by founders driven by ego and vision rather than by disciplined market research or curiosity or understanding of the market.

The successful ones will either have gotten very lucky, or know lots about the market as you say. In fact the first main success hurdle is to understand the market well enough to know it's actually a market, and that it can be monetized.

All that to say, I agree with both you and OP.