I find I rarely agree with you on these forums but these points are all completely valid.
iPadOS especially needs a bit of a UI rethink also.
Like- swipe down from the middle for notifications, to side for control center, down from the middle of the screen for spotlight.
Talk about a huge waste of space and time.
It should all be made in to one screen you slide down to access system stuff like this. Control centre aspect needs to be able to be customised with whatever you want, You should be able to access settings app from here (which you’re right - it’s a massive mess), it should slide down in a similar way, as an overlay. Notifications could be in miniaturised into a small scrollable section on the opposite side of the control centre, at the top should be search and finally it should incorporate mission control and spaces in the middle section.