Sounds reasonable approach to me. Also I'd include VPS and other cloud services too. "Is this VPS enough to run NextCloud" is a perfectly reasonable question for this community just like "is my old thinkpad good for...". I don't think there should (nor can) be a hard rule about what hardware to use. Questions obviously outside of self hosting (e.g. "what GPU I should by to play minecraft") should go elsewhere but otherwise I don't think there's even a real need to limit activity.
And also there's a half a dozen of posts here daily (unless mods remove posts really efficiently). My opinion is that even if the post could go to some other community but leans to self-hosting side of things it can stay. Maybe if there was tens or hundreds of posts daily it would make more sense to limit what goes, but as things are now I don't think any kind of (in a lack of a better word) gatekeeping is beneficial to this community nor anyone else.
Unless your ISP gives you a static address and agrees to change PTR record to your server address. Then it's no different than any other server on the internet. Obviously odds are that you're not getting one or if it's an option they'll likely charge more than VPS is going to cost you, but it's not unheard of.
But for the actual topic, I don't get the myth either. I've got a good old postfix+dovecot setup running and the only problem I have is that spam filtering isn't quite as good as with commercial providers, but the handful of trash coming trough is easy enough to take care of manually.