And why I'm suggesting they start making what the people want.
No it's what you want. The people have spoken. Nobody is buying Dex. Everyone is buying iPads.
There is little to no demand for turning the iPad into some tablet-computer hybrid.
The iPad already is a tablet/computer hybrid, it just so happens to be kind of bad at it, which is why articles like these keep popping up. Apple already has an OS optimized for pointer control, just allow macOS to load up with the right hardware connected.
If you (or anyone else) doesn't want that experience... Don't? Nothing would be a forced change for anyone that doesn't want it.
Seems to me that they are doing just fine.
They are stagnating because the market is saturated.
The iPad is a "private" device, so there isn't any social pressure to have the latest model. You're not taking it out in public multiple times a day.
The use cases are also more limited, so even when the software support ends, there isn't that much incentive to upgrade. Streaming services still work, browser works and the drawing apps work, no point in getting a new one.
I've owned iPads since the 2nd gen and haven't had a single one's battery die on me. Every time the device physically broke (after being handed down twice) before the battery died.