It runs apps on its own. So many things you might want to do on an iPad could run just on the Vision Pro itself. While I can't live without a full computer, a lot of people are happy with an iPad only. Many of those might also be happy just with a Vision Pro.
The coversation is about a MacBook Pro, not an iPad. Users of the two have very different expectations in terms of CPU, memory, storage, battery life and more.
Depends on what the original poster uses his MB Pro for and how much computer power is required. That is why I compared it to an iPad. A M2 is quite a powerful processor on its own. Any "power" user won't use the VP for computing, I guess, but it could well hold its own against an aging MB Pro, as long as the kind of software used it supported at all.
My M2 Air runs circles around my Intel MB Pro I am using for work. So the VP would certainly be faster, but probably not run the software I need. But then, maybe there will be an Emacs optimized for the VP :)