I'm not saying they don't make a difference; obviously they do, and obviously they would be pointless if they didn't.
What I'm asking, rather, is whether you really think a player who won a given game would have lost that same game if they had not used the "best" commander available? Do you really think that commanders make so much difference that they change a defeat into a victory and vice versa? I'm not convinced that is really the case.
Definitely some of the time, it's hard to say about 'most' of the time. There's no way of knowing to be honest. When Ostruppen came out and were 120-160mp, came at T0 and you could call in a unit every 30 seconds, they were absolutely unbeatable in 2v2 on some maps unless the Ostruppen player was utterly terrible. You could literally stick them in every building on a map. HelpingHans convinced himself this was some kind of genius strategy...
I understand the commanders are better now but still not to the point there are no banned commanders in a tournament.
Also, this is a full price competitive multiplayer 1v1 RTS. You shouldn't be having to put up with FTP Moba microtransactions in this sort of game.