Of course regular window management doesn't just work out of the box, you should install one of the many different window managers on macOS.
I was under the impression that to get a product that just works, I can buy Apple hardware, right?
Ultimately, Apple is responsible here but I don't think this is an intractable issue baked into the software. And yeah, maintenance is required despite what the perception might be. Apple even offers great support services for people who are not able to do it themselves.
Does it even matter if it is a corrupt setting or not? Why would it matter? As far as I am concerned, I am seeing every iOS user around me suffering from this. The root cause does not matter here.
Throwing random nonsense about 'general/keyboard' settings (that don't exist, btw) because you yourself can't think of anything specific should have been another.
The keyboard, specifically the Autocorrect, is fucked and has progressively worsened over the past 5 years. It's atrocious today. This is a first party problem that shouldn't need 3rd party solutions, end of story.