That's not really the way it would work, if the Many-Worlds interpretation is true. We flatter ourselves to believe the universe cares about our thoughts and actions, but really, as far as physics is concerned, we're just clouds of interacting particles. It's not human decisions that would split the quantum state of the universe, but quantum-level events. Human thought and action are classical, involving far too many particles for any quantum superposition to persist. It would be fairly rare, I think, for a quantum-level divergence to have a recognizable effect on a human scale. Maybe certain evolutionary mutations would happen differently (including mutations that produce diseases and pandemics, affecting human history), or someone might get cancer in one universe and not in another. Maybe once quantum computers are invented and start having an influence on people's decisions, then divergences on a human-discernible scale might happen more often. But it wouldn't be every decision.
Even aside from that, it's simplistic to assume that every decision would be made more than one way, as if they were all just random coin flips. Usually we make a given choice because we have a specific reason to make it, so there wouldn't be any universe where we arbitrarily made a different one. Even Doctor Who: "Turn Left" had to go to some lengths to contrive a scenario where Donna was equally likely to turn right or left, because that's not something that routinely happens. For that matter, even a coin flip isn't actually random -- it's just that we can't measure or predict every single microscopic force that's acting on the coin to determine which way up it lands. Even a decision that seems random is shaped by its context, and thus may actually be deterministic.