Relatively new user here. Love the game, but I almost dropped out my first season when I was put into a league with mostly bots and/or neglected teams. I signed up for a basketball manager game to play against other real humans, and basically had to wait three months to promote to even really figure out what the game was all about. I decided to stick it out until I promoted to a more competitive league (which I am very glad I did) but a person with less patience than me might not have even started.
Besides the obvious of getting more people to sign up, it would be interesting to see the percentage of users who stick around when they get put in a competitive league vs a user put into a neglected league.
Lastly, most of the forum advice seems to focus on training which really delays the excitement of trying to build the best team possible. The transfer market is definitely the most fun and interactive part of the game, in my opinion, and if more people stressed working the transfer market, rather than training, new users might get more immediate satisfaction and incentive to stick around.
Anyway, just thought I would give my perspective coming from someone who just recently started playing.