Can you please read what people say? forget about Hornets. Hornets are T2 Bombers. They are not fighters, and my comment isn't talking about them. My post is purely about basic fighters vs basic anti-air. Fighters cannot kill anti-air. Individual anti-air kills individual fighters which flies directly through its targeting area. In a fighter vs fighter battle, land AA do not need to be replaced. Generally bombers move in to attack the target, fighters move in to intercept the bombers, fighters move in to intercept the interceptors; and if AA is present, you need something to shield the bombers. I'm not saying "The only way to defend your army is to use t1 AA". But having t1 AA means that if the bombers first pass is a failure, you aren't completely helpless while the second pass is made. Metal costs are fairly pointless. The only time metal costs matter are when you are going from a build rate of 100% to a build rate of something less than that. Spinners take less time to build than hummingbirds, and time is much more important than metal cost. In addition, for me anyway, spinners come out of the land budget, not the air budget.
I did read your post. And if you read my post, I started off by pointing out how ground AA is ineffective both in time and metal cost per DPS against fighters. It does have the added benefit of not being shot at by fighters, but that benefit means nothing if the ground forces cannot catch up to the fighters. I did read your post. I did respond to the points on your post. I then went on to expand and make additional points that were not factored into your post.
Lately all my games seem to end with one guy building a ring of Pelters and AA around his base, massing Hornets and Hummingbirds/Peregrines, and then throwing all his build power into nukes. If I'm close enough to someone I can deal with them early on, but when they're on the opposite side of the planet from me, it doesn't matter how many ground units or fighters I send, they just get shredded by hornets and defensive nukes before they get close. I really can't figure out how these little bases can sustain the kind of industrial output they do though.
I think it's mostly a question of focusing their construction. While you're building tons of units, representing quite a lot of metal output, which is unlikely to accomplish anything, they're building planes that rarely die, defenses that rarely die and are just throwing nukes at you, which are pretty much always worth their cost because nukes can't really be stopped. Even if you have a ring of anti-nukes, they can either overpower one particular sector or just creep around them or, as I've seen, actually kill your anti-nuke by edging their nuke shots closer and closer until the perfect distance is achieved: the anti-nuke fires right as the nuke hits the ground and this is close enough for the anti-nuke to get destroyed in the blast. I've definitely curbed my playtime until they put in new units because the game right now is basically nukes + planes. Ground units are good for harassment but it's REALLY easy to stop hordes of ground units with relatively little cost. You could also artillery creep them, which works well enough, but it's 10x the micro of nuking and easier to counter.
You forget aa units are less vulnerable to mt rolling in a battalion than fighters. Still making them plenty viable imo. So increase their range and problem solved
I just lost a game... to levelers, after having defeated an air opponent. ...and the only reason I lost to levelers was because I didn't go for at least t1 air (at least not quite in time, I had 2 bombers up when they rolled in, 3 more and I could have hit levelers unopposed because he had no AA tanks). The air opponent was easier. Perimeter and early harassment slowly digging in with artillery. And it is rather difficult to fight air with artillery, lost many a battery in trade to his air bumrushes.
But it's not. Fighters can not fly through the mobile AA bubble. T1 Bombers can barely drop their bombs before being shot down. You don't use AA to intercept fighters. You use AA to enforce a no fly zone where your fighters have the advantage, to ward off small raids and to buy time for you to get fighters there. If you make T1 AA more powerful the equilibrium shifts in its favour. All that's needed is some T2 AA which is able to attack multiple targets. Bombers should be able to drop bombs on an area protected by AA, because otherwise well fortified areas purely become an area where only a nuke or artillery structures can attack.
The way it is with ground units, is that a turret can attack and kill often units coming in, however a fair cost in units can get through and attack the turret back and make quick work of it. That is a measurable thing right now, the ground units vs ground turret. If we can get that same cost be what happens between air and air-defense, if it isn't already, technically we can call it more balanced then it has been.