The problem is very simple.
The full power of InDesign is predicated on the ability to access a file system. Best practice with InDesign typically has a minimal base InDesign .INDD file with externally-stored assets (images, vector artwork, fonts, etc.). iPadOS assumes that a program's assets are stored with the application itself or that the application relies on cloud storage. Then there are the issues of fonts, ICC color profiles, spot color definitions, etc.
It was actually much easier to have MacOS <=> Windows compatibility for InDesign (which was there from day 1 for InDesign 1.0) that it would be to have MacOS <=> iPadOS compatibility!
And in terms of actual use, of all the Adobe applications other than FrameMaker, InDesign is generally text intensive which certainly doesn't bode well for a device that doesn't have a native keyboard and for which the add-on keyboards are generally anything but industrial-strength and ergonomically sound.
By the time you are done getting an iPad Pro with a “large” screen along with an accessory pen as well as a keyboard, you might as well get a MacBook.
In terms of M1 chip-equipped Macs, I would strongly recommend not attempting to run InDesign on such systems using Rosetta 2. An ARM-native version of InDesign is in development and should be available in the not too distant future.