I know many have written that they have issues with multiple windows on the iPad, but for me it's never been better or easier. My main gripe is keyboard behavior which is very buggy, but not related to how easy/hard it is to make and move apps around the screen.
The fact is that the iPad is only useful because of its software. In my case it'd be useless without Files, Working Copy, Blink, Wireguard, and Screens. Only 1 of those is built-in and still it's a fairly recent addition. And it's the latest version on iOS 13 which is really the version which turbo-charged using many apps together easily. I use these apps to pretty much avoid directly using my "real computers" as much as possible via VMs or remote access via Wireguard.
But, I think we're only seeing the beginning of the iPad. I can relate to the feeling that "we should have more of what we expected by now", but the fact is that designing these power user interfaces, actually redesigning them for touch while making them compatible with existing ones, is very difficult.
A great example for HN is how we develop like we're in the 70s with text terminals and executing commands. Where on the iPad it might make more sense for the terminal to be rich like a REPL where commands/expressions act more like the results of a Shortcut (rich data, not just text) or code might be edited as an AST instead of the text which allows the concept of a "source file" to go away and instead there be a source database. Instead of trying to rebuild the editors we had we build something else designed for testing, iterating, and managing the AST. Dark[1] is a good example of this, but currently focused on the web.
This is all way out there right now, but it makes me think that the iPad is still just getting started.