I think you need to use your imagination more, there are many ways to counter airships. What about airships of your own?
Let's say they changed swordsmen so that they got a +100% bonus against all non-swordsman units. By your logic, "build swordsmen of your own" is a "counter" to spamming these new swordsmen that can't be countered by any other unit. Hardly "using your imagination." Furthermore, in my example there, counter-spam is a
more legitimate counter than what you're suggesting, since at least counter-spamming would allow you to fight and destroy the units opposing you. Building your own airships just allows you to hurt their units as much as they're hurting yours. You can't actually stop the airships.
Doesn't that effectively counter enemy airships by damaging the enemy stack as much as yours? If you dont have as many airships in range as the enemy, that's bad strategy on your part.
Oh, so I should spam forts on my borders?
Another counter for airships is not attacking until you get SAM infantry, beeline it if you must.
The "TECH FASTER" argument rears its ugly head again. Let's go back to the example above with the swordsmen. Let's say that four techs down the line, there's a unit they add called "anti-swordsman," which has 5 strength and gets +300% vs swordsmen. Now there's a counter for those crazy swordsmen built right into the game! So now those crazy swordsmen are fair, right? I mean sure, you need to already be dominating your opponents to get them, but they're there! Just don't fight anyone until you get them!
Another counter for airships is using a GG on a Woody III axeman early-game barbslayer to give him the Medic III promotion. Put him in your stack, and your troops will be able to heal the airship damage.
If I stop moving, thus allowing them to hit my units again. Nope, not a counter, just a mitigation of the damage.
Another counter for airships is beelining to flight.
TECH FASTER! ALWAYS DOMINATE EVERYONE IN TECH ALL THE TIME! ALWAYS PLAY AT A DIFFICULTY WAY WAY WAY LOWER THAN AN ACTUAL CHALLENGE!
that's what makes airships good, its an added element to the game in that era.
No, adding things "just to add an element" is a
bad, awful plan that
all good game designers avoid like the plague.
Airships are basicaly a rifleman/cavalry rush nerf, and it's not badly implemented because it allows the civ that went the "scientific" route (Scientific Method, Physics, etc.) to have a chance to survive the rush of the civ that went the "military" route (Military Tradition, Rifling, etc.). It slows the rifle or cav rush down because if you want a level playing field and don't have a tech lead then you've got to research physics too.
Hey, we should also add un-counterable units to other "scientific" techs, too, then, right? Alphabet surely needs some kind of über-unit so that players who go science shouldn't get punished, right?