Occam's razor, because it seem it is often used wrong by using it for just shutting down possible explanations. Typically noone mentions, that this is about guessing probabilities without prior knowledge and not a way to completely ignore an explanation.
Yes, it's a way to move forward with incomplete knowledge, when you need to make assumptions regardless of which theory you go with. There will always be an asterisk by theories or decisions made with this method, because one of more of the assumptions themselves could later turn out to be incorrect, thereby invalidating your decision. Occams razor is very misunderstood and used or quoted incorrectly all the time.