comparing small communities or forums as primarily similar to the caste system is certainly a take...

The world is not better when everyone is exactly the same, it's better when everyone has a place they feel welcome. For some people they enjoy reddit or discord, others don't. There's nothing wrong with someone preferring something made out of passion, rather than something made to make more money.

>it's better when everyone has a (place?) they feel welcome

Yes, the problem is that the overwhelming majority of people using sites like Reddit or Discord are not choosing it. They are there because it has become their only alternative.

And it has become their only alternative because all these hobbyist forums can only exist when they are serving some tiny, exclusive priviledge few. If they grow too much, they either will crumble or will find themselves becoming a "professional" service with people on payroll and revenue targets.

> can only exist when they are serving some tiny, exclusive priviledge few

I'm not sure I agree with this, but it does fit the pattern. Auto forums are an example of this working. But I wouldn't call that a privileged few, would you?