Explain how MMR is fair...you can't

The onus is on you to prove that it’s rigged.

Also, e-sports does NOT have randomly generated teams at all. Teams scout and sign players, and if the players can’t perform, they’re out of a job.

Everything Blizzard ever said about Competitive and its matchmaking is compiled here:

People ignore it though, or flat-out say that the dev team is lying, because they want to believe that matchmaking is rigged.