You ever visit
http://reddit.com/r/unixporn? Or see ZorinOS or Xubuntu? They both run Xfce with a more updated skin. Changing the WM and DE in Linux is as easy as changing your socks and is not a real comparison.
Again, not a fair comparison. Web browsers on iOS are hamstrung already because they must all use Apple WebKit and not their native engines like Blink or whatever Mozilla’s new version of Gecko is called. They are effectively just wrappers for their sync tech so you can have your Chrome or Firefox bookmarks/passwords/etc.
If you really want to see a powerful iOS program, just look at any of the iWork apps. They are 100% the same features you get in the Mac versions. Check out LumaFusion video editor. Broadcast quality video editing that is on par with Adobe Premiere. Check out
https://affinity.serif.com/en-us/designer/ipad/ and Photo for their iPad apps that are 100% feature parity with their Mac and Windows versions.
There are many complex iOS programs out there. The iPad has proven can get work done, and any of those programs can be refactored quite simply to run in Catalyst already; they won’t even need that to run on Apple’s silicon. But did you even watch the keynote where they used photoshop to open a 5GB PSD on an A12Z chipped Mac? Literally the whole keynote was demoed using their new OS on their SoC. Its still a Mac, you will still be able to get programs from anywhere, you will still be able to brick it if you delete KEXT files or Bork the wrong PLISTs.