I think that much of the bugs we, as long-time fans of the game, despise are mostly noticeable/irritable because we've been so involved and can recognize them. The reviewers who are new didn't notice them as much, or otherwise overlooked them assuming some of them to be legitimate physics quirks. More travelled reviewers probably felt nostalgic, and didn't believe that they took much away from the overall experience of the game, keeping their role in the score low. Non-specific scores probably compound this, as Cpt. Kipard notes. Graphics don't matter so much in sim or simlike games such as KSP, and thus play less a role in the reviews. I would agree that the game isn't well polished, but parts of that were likely taken into consideration.