There really isn't a "main skill" in BB.
I don't think the answer is to speed up the "end of the game." Players will eventually reach their peaks and decline, it is only seaosn 6, give it 4 more and you will see what they had been reaching for this whole time.
It would also be more realistic for players to start slowly declining when they hit 28-29. How many 32/33 yr olds do you see who are still as good as when they were 27/28?