I didn't read all the posts and I'm late but here's why I play less than I used to: There's less to do that's fun and interesting.
Most of that IMO is related to the consolidation of strats. I use to like to bomb strats with both bombers and attack planes, rocket strats with Skd's or PT boats, shoot strats with tanks or mobile flak and defend strats against others that liked to attack them in many different ways. Most of that is gone.
All of that used to spread people across the maps. Now they horde more than ever before because there's little else an individual player can do alone to effect the outcome of the game so 1:1's also declined as a result. So did buff hunting. Fewer targets = fewer buffs in the air. Now you get to fly with or against the horde or fly for an hour going after the one guy who thinks a strat raid makes sense but might bail before you reach him.
There used to be a time base taking (or defending) wasn't that difficult that it needed 40 planes un the air. The additions of star wars ack, bigger towns, spread VBases, etc,. etc., etc, only encouraged the horde. I swear the horde is exactly what HT has aimed for over the years and he's succeeded brilliantly (The blue line experiment would have been the ultimate manifistation of this).
There's more but those leap to mind.
I still keep my subsciption but play less and less and less. It's only a matter of time before it's never at all and my subscription is dropped.
RIP AH.