Yeah, Valki said groundfiring subs is part of the meta. You incorrectly read that as "significantly shaping" the meta. Things can also be a small part of the meta. And the point here is that they are a small part, because subs suck, because groundfire exists.
I saw your argument, and I don't think it would make game balance worse. You're saying, we make a change that BUFFS subs, but they are still vulnerable to torps, so air and torps become more important because that will now be the way you have to counter them. Well, that's the point. Removing groundfire still only makes subs more viable, because you CURRENTLY can torp them just as easily. It doesn't sound like you think removing groundfire would make subs OP, just that this would only help make subs slightly more viable. Well, slightly more viable is better than zero more viable, when they are already significantly underpowered...and giving a small buff to an underpowered unit will improve balance rather than make it worse.