While there definitely is more to the game than just grinding stuff, I do have to say that it feels kinda disappointing going to the results screen after a match and seeing that you got absolutely no EXP.
Personally, I think you should have infinite level ups again, but you only get the limited number of mystery boxes per day and, after that, you only get a significantly reduced amount of cookies (500 or 1000 or so?) per level up. As such, you continue to get rewards if you continue to play, but you're encouraged to not play the game as excessively.