Uh. I assume quite the opposite, actually. ACM isn't just about close-in manouevering. All those moves are tools used to position you for attack or defense in a multi-plane environment.
Sorry for the overlook.
But quite frankly, the scope of "ACM" people talk about in this thread is sometimes wildly different. Some people specifically point out ACM as close-in maneuvering, a means to continue pursuit without breaking away or coming in for 2nd, 3rd passes. On the other hand, the ACM you're talking about is a very wide concept, which I think it cannot be described as just "ACM".
There is one big drawback to relying on gunnery alone which is unique to AH (and games of the genre): you're relying on steady connections for you and the target. Rule #4 sayeth: "Warps: The Great Equalizer." I can't tell you the number of times people I fly with - who land 5+ kill missions routinely - end up dead because some bogey just couldn't be hit due to some blip in the Internet.
That's a no-go Dok

Warps and conn. issues effect everything in the game, not just gunnery. Close and maneuver all you want and sometimes the plane would warp away, and you'd have to start maneuvering all over again.
Again ... IMNSHO you need a combination of SA, ACM, and gunnery to be a complete A2A pilot in this game. Whichever one you excel at will govern to some degree your most successful style of play. Whichever one you suck at most will govern to some degree the reasons you get shot down most often. No one is more important than the others in the big picture.
Agreed.
But the Earth still rotates and gunnery is still much more important than ACM.
Let's try fantasizing a duel between a pilot who can get 99% of shots in but sucks in maneuvering, and a pilot who will outmaneuver 99% of people in the world, but has bad gunnery. Who'll win?
As funny as it seems, these things happen a lot in H2H rooms

Try the H2H games some times - lot of fun options. Turn the lead-computing gunsight on and you'll notice there is basically no such thing as "ACM" in the rooms. Every first pass is a death pass. On the other hand, in a room full of newbies, I'm the superace when I take the Zeke up. These newbie guys will always turn.
So, in a H2H room full of newbies with lead-computing sight on, I can beat those guys all day long without using the LCS, until one actually discovers that they can use the LCS. So what happens if a total newbie with a LCS engages me not using LCS?
If he is higher than me I'm dead. If we both approach in a HO merge I'm dead. If I bounced him unnoticed, I win. If he sees me bouncing and comes to HO me, I'm dead. If I have an alt advantage and rope him with at least a distance of 1.5k plus max closure, then I might win. Basically, if he has his gun pointed at me inside 1k range, and knows how to control the joystick, whatever angle, whatever situation, I'm dead.
A person with perfect ACM still needs some gunnery. A person with perfect gunnery doesn't need ACM at all.
ACM helps the kill. Gunnery, just kills.