Funnily enough I prefer the way command points get generated and used in AoS and 40k Killteam compared to main 40k. Also bravery/LD/morale/whatever it's named has it's issues in 40k as well. Even if you play an army that can stack a -8 modifier to the LD it's not worth going for such a tactic at all. The last Warhammer I've played where LD mattered was WHFB 7e and there in fact it was pretty much the core mechanic for how to win fights and the movement phase was what decided whether you can win the fight or not. So an entirely different beast than AoS and 40k today.
You say you don't like flavourful rules like the slaaneshi combat thing or Nighthaunts ethereal thing, but something like that exists in 40k too. Like the Genestealer Cult deployment shenanigans and daemons having basically the same as Nighthaunts in that they all have a 5+ invulnerable save which completely ignores armour penetration and is only not as much of a problem due them being 90% melee which sucks in 40k and 40k throwing around enough dice to not care about a poor defense like that.
AoS being melee focussed may not leave much room for errors, however the other side of the coin is 40k being so shooty that whoever goes second can pick up a bunch of his units before having been able to ever use them in the game which can quickly snowball into a win for whoever went first with the more shooty army.
Feels to me like this is mostly a case of "the grass is greener on the other side".