that would never happen to any commercial social media service out there.

Actually it does. Lots of people used to talk to the dude who started Twitter and he would respond. Making "important" people accessible to randos like you or I was kind of the major benefit of the whole service, especially in the early days.

Likewise, I've personally had comment chains back and forth with /u/spez on Reddit on many occasions, and a few other notable admins, founders and CEOs too (keysersosa, aaronsw, yishan and kn0thing spring to mind) although they weren't necessarily CEO at the time.

That said, it certainly is nice when communities can stay small enough to still have regular interactions with each other, admins and users alike. And fediverse is designed to promote exactly that. These huge communities like lemmy.world and even lemmy.ca are sort of a sign we're not using it quite "right" and we're still following the "centralized" model, but that's okay they are serving an important role for now and will continue to serve an important role probably forever, but hopefully never too important, and it will always be possible to break out into smaller more specialized communities but still stay in touch with these bigger ones.