To-hit chance, staggering mechanic and severe dumbing down of morale system prevent me from enjoying the combat as much as AoW3. Then there's the ubiquity of aoe attacks which spoils the encounters and makes ai do really dumb shit all the time (also wrecks the autoresolve for some factions/units, which is a rather big problem when it comes to pacing). Flying unit making a comeback is a nice change, but doesn't really offset much do to huge focus on ranged weapons. The combat is still pretty damn good, mind you, and you're absolutely right that the variety of units, secret techs and mods is really cool and the biggest draw of the game by far.
I hope they will make the strategic map more varied and interesting with the coming DLCs.
They tried to do that with patches and the first dlc, so they see it as a pain point, which is good in theory. In practice, they had very little success so far imo and to make the strategic layer actually enjoyable they would need to heavily revamp, if not outright drop/replace, entire systems like city building or sectors and I don't think that's very likely.