[I suppose that quote was sarcastic... but in case not, let me add a few things:]
Oh! My list is looooong!
* Multiple "window" support sucks.
The way iPad OS handles multitasking between several apps and windows is very unintuitive.
I always end up tapping the wrong widget or wrong edge and suddenly I'm in spilt screen, can't get rid of the second screen and whatnot.
If all I want is to make one application's UI (window) smaller, so that I can put it aside, but have it still visible onscreen so I can reference its data in another application that I want to have fullscreen to work on, that's troublesome on iPads.
On a personal computer this is very easy, just resize the first application window small while keeping the important parts visible, then shove that window to edge of the monitor, switch to another app and resize that window to a size that keeps the previous smaller window visible.
On the iPad it just feels tons more clumsy and complex to do the same simple task.
* Multitasking of apps sucks.
While the iPad offers picture-in-picture for e.g. YouTube videos, I find that the iPadOS interferes too often and ends up interrupting or stopping that background video. Because either the front app could also play video and therefore just stops any other picture-in-picture video task. Or a website has autoplay on, which forces your picture-in-picture to stop.
On a personal computer video in another window just keeps playing, even if the front app plays some other video. They can play both at the same time. On the iPad this is nearly impossible to do. Try having 3 browser tabs with videos playing all at the same time! Often not possible.
Sometimes I deliberately want this. E.g. playing some music in the background, while waiting for a streaming video to start while chatting with a friend on Google Meet to discuss the streaming video together. Easy on my Mac. Never managed to do that on my iPad...
Then other apps that I deliberately have running in the background on my iPad for notifications get auto-shut down by the iPadOS after e.g. a month of running. If I don't constantly bring these to the foreground to keep them alive, they just die on my and so do all its notifications... Ugh.
* Notification handling sucks.
While it is nice to have notifications like on a phone, they always interrupt, and when dismissed are gone who knows where, more often than not I am unable to get back to them, or they automatically decide to snooze and show up again some minutes later, with no control whether you want to snooze them or not. Often they do not show up in Notification Center or don't provide the control that one would want.
Somehow notifications seem to work much better in macOS.
Notifications on iPad feel clumsy to the point that I often switch as many of them off as I can - just to avoid having to deal with them.
* Manipulating data in several applications seems much easier on a personal computer.
The iPad's clunky "Files" system makes it hard to locate files and keep them organized. Often you open it up and it just shows a big video full-screen or some other file that you need to close first - while all I wanted was to see and locate some files. The "Files" application should not also be a viewer application, that should be handled separately.
On a Mac I can just keep all apps I intend to use together open and visible at the same time, in windows next to each other, where I can then easily save temp files on the desktop or use copy/paste to transfer the temp data into another application, and then on to the next application etc.
On the iPad I need to store it in Files which may not even be instantly available, having to close a few viewers first, not all apps support it properly, or when copy/pasting sometimes content ends up without styles, ugh... that kind of multi-app workflow just never worked for me on the iPad. It is seemingly a massive amount faster and easier on a Mac.
* Preferences and Settings are all over the place.
The way some settings are in an application's own preferences, others in the iPad Settings under the application name, and yet still others in some completely different location.
For example I always get confused as to where do I switch my Apple Music login ID? Why is it not in the same place as with Music on macOS? A lot of other iApps have similar chaos in regards to where which of their settings are...
* Have you ever tried switching users on an iPad?
Sure, Apple even says that i-Devices are not designed for multiple users. Fair enough. But then they geo-fence features or support them only in certain apps or OS versions that this simply requires users to create several Apple IDs to be able to do all the things that you can do on a personal computer easily...
So there will be situations where you need to switch your Apple ID. I have 4 by now...
Yet on an iPad this is a Royal Pain In The Arse! First you need to deactivate "Find My", then you need to delete all data, then worry about which to keep and later merge, wait for the iPad to do its thing, then log in with the other user, wait until all your stuff and settings change and are downloaded, while all your FaceTime and Messages sessions were force-logged out.
And then the whole thing in reverse, to go back to your main Apple ID. Ugh. No thanks.
* Intransparent settings.
Speaking of Apple IDs on i-Devices. My "Music" app on iPad has no user signed in, all web downloads, Siri settings, radio etc. are switched off. Still, every time I open "Music" it attempts to connect to some Apple servers and complains that no user is signed in. Why? Where can one switch this off? No idea. This is not transparent. Ugh.
* Seemingly enforced subscriptions everywhere.
Everything in iPadOS more and more becomes a "subscription" service. What if I don't want that?
People often end up paying for stuff they barely use or not even use at all. It's getting bad on Windows and macOS too, but it's really bad on iPadOS. Apple is pushing hard to make even many features of iPadOS a subscription exclusive.
I think I stop here. But I could go on for ages...
You hopefully get the picture.
iPadOS is just really clumsy to use and in my opinion totally unituitive and incoherent - at least when you compare it to most personal computer OSes.
The iPads M class chip is amazingly powerful, and could put many desktops to shame, but with iPadOS all that power goes to waste, I feel...
There are a few individual apps that certainly profit from the M class chips, but the way iPadOS, apps and data are handled and interact is just not worthy of all that power, I find.
It depends on your use cases, of course. So your milage will vary.
And I understand some people love iPadOS.
Me, I just can't stand it. Going back and forth between Windows, macOS and iPadOS, every time I use iPadOS I just feel like I'm put into a straight jacket... Nothing works quickly. Nothing works as one would expect. Everything feels clumsy, unintuitive and all over the place.
p.s.
With the iPad's CPU getting more and more powerful, Apple tried to find ways to make the iPad able to use that immense power. Fair enough.
But at the end of the day iPadOS is still derived from a phone operating system that was at its core designed for 3 1/2 inch multi-touch screens that could handle a few smart apps. The design language of that operating system was never intended for powerful features like multitasking applications.
When Apple moved iPadOS out of iOS, they had a chance to completely redesign it, to allow it to handle more powerful features.
Yet either Apple did not have the manpower to redesign iOS for iPad properly, or they lacked ideas how to even do this, or it was a political decision to keep iPadOS close to iOS in design - either way, in my opinion that transition from iOS to iPadOS failed completely.
All we got was iOS with a few "Frankenstein'd" features bolted on that just feel unintuitive, rather than getting a new powerful multi-touch OS that can support and handle powerful handheld hardware.
