You address only one issue not the whole "problem". There are teams with 22-0 ,21-1 etc who are competitive and for whatever reason they lose the play offs (opponent buys very strong players, they make mistake in tactics/enthusiasm etc etc)The new rule is better because more people are happy, it brings more money to the market and it makes the game more interesting for new managers that promote from IV even by accident sometimes. From the motivation perspective you are right but all the other negatives that occur simply overshadow this propositionManagers should realize that there is no perfect system that everyone is content and everyone thinks its fair. But in the past few seasons solid progress has been made so that the game is more enjoyable and fair for newbie managers as well as old ones.
One solution might be to not have the team that secured promotion play the playoffs and give that spot to another team, but that would be difficult to implement.For an hypothetical financial gain once upon a time, I wouldn't want to not have a chance at a title, be it of a lower division.Also, those auto-promotion spots can benefit to other teams if the ones above them do win their division.I think we are making too much out of it.
One solution might be to not have the team that secured promotion play the playoffs and give that spot to another team, but that would be difficult to implement.