But you have to use it to counteract the intuition that only one universe is simpler. Occam's razor is a formal way to tell you, "hey your intuition is wrong, the other theory is the simpler one!" And for it to be useful to you, you can't just allow yourself to say "oh it is just a heuristic" when you don't like what it says. Instead you have to ask "what would I do if I deep down felt that many-worlds was simpler?" and act in accordance.