As a relatively new reviewer, I have a very different perspective. Quite simply, I'm not sure what the guidelines are for using or not using the Skip button are! I've intuited that I should use it whenever I'm not sure what to do, but frankly, skipping feels lazy. It feels like I should have known what to do or spent enough time to figure it out. Moreover, I don't really remember reading any FAQs, guides, help center articles, or meta posts explaining what the guidelines are for using the skip button or soldiering through to figure out how to handle a difficult review.
What I think this means is that a simple click-through or FAQ article saying that it's OK to use the Skip button when we don't know what to do with a post would take care of the problem. This will take a lot of pressure off of new reviewers and encourage them to skip more liberally.
EDIT:
On April 27, I edited What are the guidelines on reviewing? to include a tip that says,
If you're unsure how to review a post (perhaps it's outside your areas of expertise), skip it. Someone who understands it better will review it later.