But nobody looses any ability!!
The % is merely a reference point. Right? If a player has the ability 25 day 28 he will have have the ability 25 the following season too on day 1. But then someone might say that thats semantics, in lvl 1 100% was good now all of a sudden I am at 80%, and need another 20% to become good again. But even that isn't the case. 7 of 14 teams at lvl 2 will also just have been promoted. If you had 100% on day 28 and had a good team, you will be very highly ranked among your league and CL rivals on day 1 of season 2 too.
Its completely a misunderstanding to believe that your team looses any ability after getting promoted. It really is.
Nordeus should have an in-game pop-up window appear after season 1 when you get promoted explaining this. New season new standards.