He complained about the difficulty of installing an application. He didn’t complain about establishing a personal data center.
That one line will give you the Nextcloud. Exactly one more line in snap will give you a self sign cert. Alternatively, the line below will give you remote access, a domain, and a valid certificate for your application:
It seems reasonable that someone would want to go beyond just installing software; they are presumably doing so in order to use it for its purpose. Being pedantic about the nature of the complaint (i.e. "He complained about the difficulty of installing an application. He didn’t complain about...") seems to miss the point. All of the additional steps you lay out also have their own steps to get done or decisions to be made, and when it is all said and done, it seems reasonable to imagine that things could get quite complicated.
I mean if you want a working Nextcloud instance, available through VPN with backups, then no, it doesn't get more complicated than that, actually. It is incredibly easy.
There's lots more to hosting your own file share/sync tool than just standing it up.