The iPadOS does not feel like a true OS because it's a giant iPhone.
The history of how iOS, iPhone and iPad came to be is interesting. The story goes that Apple was first working on a tablet... the iPad, first... but Steve Jobs made the team take what they had built to date and make a smartphone first. That was very hard since they had to miniaturize everything from the tablet project and were dealing with many new technologies both hardware and software. In 2007, the iPhone launched. 3 years later, the iPad launched. The iPad was truly a giant iPhone, running iOS with very little to differentiate the operating system.
Today, that still holds true. For those not sucked into Apple's marketing, you could put the first iPad next to the very latest iPad and we are still using the same foundation, the same grid of icons, the same design patterns. It's still iOS with a few tricks like Stage Manager.
Where did iOS come from? iOS is like Palm OS which first came out in 1996... very much the same foundation with the grid of icons and card views for Apps:
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Where did Palm OS come from? Apple Newton OS invented it in the early 1990s:
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Obviously we have much nicer screens and more powerful devices, but iPadOS is iOS and iOS is a mobile operating system that is stuck with foundational design patterns that goes back decades... just like Windows and macOS... using the same foundational design patterns that goes back decades.
Rethinking the operating system is needed, and new classes of devices need to follow.