Dang, Mach really fought the good fight in this thread. I feel like no one who responded to him addressed the core point that ground-firing is super unintuitive and doesn't really add anything to the game. As he pointed out, if it makes sense and is intentional for battleships to shoot subs, why don't they do it automatically without this very odd groundfire + drag the order mechanic? Every other unit in the game attacks whatever it can when things are in range, why would this one behavior work differently?
It absolutely makes it unintuitive for new players, and like Mach said, 80%+ of the playerbase probably doesn't really know how this system works. There are things that add depth, but you have to recognize the difference between adding depth in a reasonable way that "feels" good for players, is intuitive, and makes sense, and ways to add depth that do not.
A good test is, "if this wasn't already in the game, and someone suggested it, would you think it's a good idea?" It may be too hard for some people to consider that hypothetical.
Along the same lines, we could add cool micro tricks. T1 mobile arty deal double damage if you control+k them before the shell lands, just like Age of Empires. Sounds super fun, way more skill! How about ASF/Inties can target a plane that's far away, then you hit the stop button, they'll fire their missles at targets on the ground near them?
No matter what, if you think battleships, fobos, and bombers should be able to hit subs, why would you not just allow them to target them? If you think having more micro "skill" is a good feature, why not have other units be unable to target things unless you groundfire? Maybe t1 mobile arty can't shoot units unless you groundfire+ shift-click?
It feels to me like Mach is being so reasonable and clear here and people want to find the most convoluted/semantic ways to defend this behavior, when it's obviously extremely unintuitive and doesn't fit in the logic of the game at all.
I'm not saying you should necessarily get rid of it, maybe it is too big an undertaking, and I'm no expert in naval balancing. But acting like it makes sense the way it is is just silly.