But I believe "good data scientists" are usually PhDs with a few years of experience.
This is the same argument that says only people with CS degrees can be good software engineers. That is provably wrong because there are good software engineers who don't have CS degrees. Good data scientists are just people who can do data science well. That's the only valid measure. Having a PhD and some years of experience increases the likelihood of that being the case but having those things doesn't automatically mean someone is good, and not having them doesn't automatically mean someone is bad.
This is the same argument that says only people with CS degrees can be good software engineers. That is provably wrong because there are good software engineers who don't have CS degrees. Good data scientists are just people who can do data science well. That's the only valid measure. Having a PhD and some years of experience increases the likelihood of that being the case but having those things doesn't automatically mean someone is good, and not having them doesn't automatically mean someone is bad.