Mac OS was great pre-Mac OS X. Revolutionized personal computing. Did wonders for Windows and Linux as well. But it had inherent limitations that inhibited further advancement of the Mac platform. Mac OS X overcame all that and basically revolutionized personal computing all over again. It was a massive advancement for the Mac and for every desktop computing platform out there.
iPadOS, for all its faults, is still a fantastic tablet operating system. Has been great since iPhone Software 3.2 on the original iPad. But it has inherent limitations that limit what it can do as a computer. Again, I'd argue that on every iPad still rocking an A-series Apple SoC inside, this is still fantastic as those iPads are perfectly marketed to iPadOS's capabilities as they are today. But, for M-series iPads and for the kinds of experiences Apple markets those products as being able to do (e.g. Editing seriously in Final Cut Pro, running multiple Apps at once, effectively replacing one's PC Ultrabook or MacBook Air as their next computer, etc.), there's room for more capability.
This doesn't require macOS on the iPad in any capacity. Nor am I advocating for anything even remotely like that.
If it requires iPadOS to fork off a iPadProOS, ProOS, iPadOS Pro, or anything of a similar sort, then, honestly, cool. Leave the media consumption use cases to the standard A-series iPads; standard, mini, some incarnation of "Air" (whatever that means for iPads in the present era). Overhaul the capabilities of iPadOS on M-series iPads; give it multi-user support, give it desktop-class multi-tasking from top to bottom, Terminal and Disk Utility support, Xcode (if Final Cut Pro can come to M-series iPads, why not Xcode?). Support for desktop-class extensibility using the same frameworks macOS has (again, without making this all just macOS on iPad).
Steve Jobs originally saw the iPad as the thing that fills the gap between smartphone and computer. I can say from experience that, while some multi-iPad configurations make less sense than others, the mini and the 12.9-inch Pro have each proved that even in between iPad and phone and in between iPad and computer, there's still room for yet other flavors of computing. I'm not too sure what can be done to further perfect what exists between normal/mid-sized iPads and smartphones (e.g. the iPad mini), there's PLENTY that can be done to further perfect everything between that and a computer.