The D&D 5e ruleset from my understanding is based around a level 20 cap, so why would they choose to not keep that system which is already defined in the players handbook?
Maybe because the remaining levels will be for part 2?
Also, if I am only able to level my character 10 times total in a 100+ hour cRPG play-through, I for one would feel pretty cheated.
I expect you will be far from alone with this sentiment, but I'd say enjoy the ride; playing the game itself should be part of the reward. I'm glad to see they are distancing themselves from the trends of video RPGs (e.g Diablo).