It doesn't necessarily mean it was a team-abandoning mistake what you did. Surely things could've been better, but there are some nice things to consider.
- If you win the league you will get + $550k ($100k for winning the finals + $450k promotion bonus).
- New teams don't pay salary floor. So if you clear most of your high salary players before the Monday financial update (sell/fire) your finances will look much better.
- in Division 3 your TV revenue will be probably +30% higher.
- in the first 1/3 of the Season, promoted teams experience boost in the arena attendance and fans will tolerate your team losses. You will be selling out your current Arena seats at higher prices (maybe close to max prices for Bleachers and Lower Tier since you haven't upgrade them at all; I would have liked to see you upgrading those departments instead of the Luxury ones entering higher Division, but it is what it is). Obviously you should put focus on your Arena going forward.
- If you win at least one game during the first 1/3 of the Season, you will not experience arena boycott entering the second third of the season. You may be able to construct a roster capable of getting a win (or two) in your first 7-8 games.
- About trainees: You don't necessarily need to start your training with 18-19 years old players and high potential. There may be some 21 years old players available, who are star-perennial allstar potential, and with already developed set of skills that are ready to transitioning to a different training type. Obviously not all of your trainees need to be starters for your league games - some trainees are for scrimmage games.
So all this may incentivize you to start thinking about your team management, instead of abandoning it. And who knows, one season playing in Division 3 might end up being a nice boost when you enter your third managerial season.