Would there even be a debate about whether an iPad can be one’s only computer if touchscreens were invented before the mouse? IMHO the major impediment is iOS’ lack of support for Bluetooth mice.
I think if Apple wanted to, they could take a cue from Google’s Project Crostini to add containerized desktop app support to iOS. The Pros would be smart enough to handle containers, while the normal users would probably not want nor need it.
I’ve long mused that what we really need are devices that have built-in hypervisors upon which one could run any operating environment they wished. Containers come close to this idea.