The game is carefully tuned based on the expected ratings that players have. If you drop them 15-20 points then overall results of the game is going to be affected... everything from sacks and interceptions to rushing to completion percentage. And there aren't a "few" existing leagues... every league that any purchaser created in CF20 (or earlier) that they want to open in CF21 would give wildly inaccurate results. And then we'd get lots of complaints in CF21 about how the results aren't realistic. I don't have a way of making the engine work for guys who average 75 to behave the same way as guys who average 90 in their primary ratings.
Again, I'm not saying I won't update things, I just can't make these kind of drastic changes to the numbers. It has to be a gradual change, or at least a change that I can add to a configuration option. Dropping incoming recruits a few points, and then adding more bumps to training in their first year is easy and won't affect the global engine numbers... just would make fewer freshmen starters on day 1 but overall juniors and seniors should have similar ratings to what they have today.