TL/DR: The iPad is a fantastic device and I enjoy mine, but outside of ridiculous workarounds you can mostly only do what Apple has specifically considered and allowed within its parameters. If that is impossible or in a way you'd rather not work then you're out of luck.
As has been said many times over - the limitation is the software. For many users the iPad is all they need and for many "professionals" the iPad is sufficient, but the vast majority would prefer - or honestly be better served by - a MacBook Air.
Some things I do as a "power user" that iPadOS just doesn't allow:
- Can't create smart playlists in Music.
- Can't create or view smart albums in Photos.
- Cannot act as a server - fine there are better dedicated products.
- Can run virtual machines for testing/fun
- Can't access terminal
- **Can't trust software to finish processes in the background**. - biggest issue to me.
- App Store restrictions
Just this weekend I decided that I wanted to create some custom ROMs for vintage gaming emulation. First of all, emulating games on iOS is difficult as apps get regularly pulled. To keep my core install clean I'm running macOS virtual machines in UTM to (1) install home-brew, (2) install WINE, (3) install Java. Then I get to play these fun hacks games all on my Mac. Essentially, if you can think it you an probably do it on macOS.
On top of niche use cases above, macOS just overs better day to day flexility. There are utilizes to improve screenshots, the menu bar, file extensions, etc.