Lot's of good thoughts there ...
#1 - Frustration - I too used to play 10-15 teams at a time, but every 12 months or so, I would get royally pi**ed at HAL for much the same reasons as Sheik stated (great teams getting beat by crap teams over and over again) and quit playing, then I'd get the bug after a while and start playing again. Every time I'd come back it would be a new version of ATG.
Right now I'm at one team a week and have kind of been on a hot streak, so I'm playing with house money. But if my 112 win team loses tonight in the semis after going up 3-1, I could easily go back on an extended break from ATG ...
#2 - Number of leagues - The huge number and variety of leagues ($ caps, games, variations) may well be the biggest reason, it would be nice if they got back to the basics.
#3 - Manager ratings - Sheik and MANY others have been asking about the ratings for a long time, it was fun, sure it was B.S. but it was something to shoot for and it also gave you an idea of who you were up against in a league.
#4 - Responsiveness/Transparency - Who hasn't squawked about this general issue? Tell us what we're actually playing and address the communities concerns when it's warranted.
The bottom line to me is that it is clearly not the same game as in years past.