They're not wrong in that most people aren't suited to or should be running what is effectively public services for other people from some surplus Dell R410 they found on eBay for $40.

That said, it's all a matter of degree: I don't host critical infra for people (password managers, file sharing, etc.) where the data loss is catastrophic, but more things that if it explodes for an afternoon, everyone can just deal with it. I absolutely do not want to be The Guy who lost important data through an oversight on an upgrade or just plain bad luck.

But, on the other hand, the SLA on my Plex server is 'if it works, cool, if not I'll fix it when I can' and that's been wildly popular I haven't had any real issues, because my friends and family aren't utter dicks about it and overly entitled, but YMMV.

TL;DR: self-hosting for others is fine, as long as the other people understand that it's not always going to be incredibly reliable, and you don't ever present something that puts them at risk of catastrophic loss, unless you've got actual experience in providing those service and can do proper backups, HA, and are willing to sacrifice your Friday evening for no money.