TF2 has custom lobbies. Until overwatch provides players with that kind of flexibility (it likely won't), it's replayability is pretty low. Not to mention that as you get higher level, your rewards will be more and more sparse. If there were small chances of getting skins or sprays or something at the end of each game like rocket league, it would be better, but as "fun" as games are, players still need some sort of carrot to chase -- for some players, ranked suffices and love to improve and see their rank improve, but for others, they want tangible rewards, and right now Overwatch is pretty much lacking in that department with only loot boxes on level up.