To be frank, the maps were also tiny on SM (except for sieges) and maps were always flat. Doesn't make it better though.
Tiny how?
It took your slow foot soldier 2-3 turns of walking to reach your enemy (if he didn't move), you could get 1-2 turns out of archery out of that.
Now it's that if you are in range to shoot an enemy with ranged attack, then he's in range to bash your face in.
There's also no room to back off, you're pretty much forced to engage your enemy head on.
It really feels like Fallen Enchantress in this regard, instead of AoW.
The maps weren't flat, AoW:SM even showed you the elevation numbers when using ranged attacks.
As for the combat system, I really don't see how the things you point out constitute stripping-down. Given that most units now visually represent more than a single person, misses are likely represented by lower damage due to distance, obstacles and such. There's nothing wrong with that, and it's frankly more realistic than having eight archers in a single archer unit miss all their shots while being in effective range.
You could of course explain it with multiple units, although it baffles me why they added them in the first place (except maybe to cut a piece of the popularity of multi-model units in other fantasy TBS).
Not realistic? Arrows aren't homing missles. If you want a more realistic representation of archers look at Dominions and maybe even Total War.
How's the flanking system, a new feature, somehow simpler than the flanking-less old games?
Together with unmissable damage it allows you to destroy most units in a single turn, making your units even more dispensable.
It doesn't make it simpler, but it certainly doesn't make up for all the stuff they removed.
How can AoW3's units be more generic than the previous installments'?
Models have less details in my opinion (well most games transitioning from 2D to 3D suffer from this), also theres a lot less flavour text in general.
Adressed your other points in the first quote.