If you replace "nobody" with "very few people" then the statement is mostly true. The vast majority of open source software is crap. Sure, a lot of it is passion projects made by enthusiasts, and there's nothing wrong with that from an artistic hobbyist standpoint, but the quality of the software is very low.

Good and successful open source software is, in terms of numbers, rare.

Furthermore, most good FLOSS has at least some companies providing financial support, if not being almost exclusively worked on by employees of a company selling non-FLOSS software to pay the salaries of those devs.

Developers putting in hard work to write quality software for free do exist, of course, and many of them are absolute gigachads, but they're dwarfed by those actually getting paid to write software.