For the record, the eSports-side of games (when we’re talking about leagues) has no matchmaking. Those are leagues you have to completely bust your butt to work yourself into and succeed in and advance to higher leagues, however (and this even includes Open Division, where all you need is a premade team). But I think you were trying to equate that somehow with a game’s public competitive ladder system (such as Overwatch’s).
If you were questioning the matchmaking system that Overwatch uses, everything Blizzard has ever said about it (and they really have said a lot) is compiled in this topic (check the References section in the opening post):