I definitely disagree.
As I disagree with the title. There's no such thing as a most important tech (esp not one that comes so late
). I personally consider writing one of the most important techs.
There are so many jumps in military along the techtree. Flight may be one, but personally I think rifling would be more gamebreaking.
My vote would be pottery, personally
. Granaries are arguably the best economic building in the game...and you can build cottages...
Flight isn't SO game-breaking as OP implies. I've won quite a number of games easily where the AI had it and I did not. Granted, most of these involved naval warfare, and massed destroyers are pretty dangerous to planes (the AI is terrible at using its navy and really has no answer for a naval SoD that includes 10+ destroyers and some battleships!).
It's very convenient and fast to bombard defenses and cause collateral with them if the AI or your human opponents don't have enough interception chances. If they do it's not very cost effective...maybe just use your own interception and spam missiles into their face.
And yes, there are a TON of military jumps, starting with bronzeworking
. You mentioned rifling, Dirk seems to prefer steel etc. I'm starting to like military tradition a lot as it's pretty easy to take it with liberalism and pick up gunpowder for the 12 str cuirassers provided you have the resources - very dangerous units!
My favorite military jump points are BW, IW/HBR, construction, MT, rifling, chemistry (naval power maps), assembly line, combustion, and industrialism. I use engineering as one sometimes too - trebs/pike/xbow with knights worked in as muskets show up is pretty strong and can get some mileage if you have enough hammers.
That's a LOT of jump points - and just like flight, none are going to be extremely relevant to a player from a military standpoint on EVERY map (excepting perhaps BW, due to slavery/chopping).
Because I tend to clump units for naval transport launching sites, airlifting is actually more inconvenient for me compared to using galleons or transports
. I'm probably weird.