As far as the attrition that certainly seems to be happening, I'm not sure the best solution to this part of the problem, but I think we should acknowledge it as part of it: Too much of the play takes place at low levels, where the game is less interesting, because teams fold or reset.
My best idea was to have people have to pay for the first three seasons when they start a team, and pay anew if they reset. They could even make seasons after the third cheaper due to the extra revenue they'd get from people who'd otherwise play for one season and fold or whatever.
I'm not sure that's the best solution, but I do think that if all a lot of agents see is Rookie-tier games, those games will look too much like little kids' trying to play football and will turn them off to the whole game, when later tier games really do look and feel enough like football (at levels we like to watch) that it might make a better impression on new players.
I wouldn't mind just skipping Rookie entirely, starting everyone out as what's now called Sophomore (still calling it Rookie), and all-- if a way could be found to do that and keep careers the same length-- because even at Sophomore it's starting to look more like high school football rather than Pop Warner, and all the awful play we now see at Rookie wouldn't exist to perhaps turn potential players off.