Nicely summarized. I see this pattern playing out so frequently that I'm at the point where I'm starting to think no one bothers creating content or communities without an eventual commercial angle that ruins the intent of the first iteration.

In terms of your notable exception, I'd say Indiehackers (now owned by Stripe) is still quite good. But perhaps that's because Stripe appears to be pretty hands-off at this point, and of course that could change.