In my opinion, the best beta readers are fellow writers, partly because they may have insight others don't, but partly also because you can agree to trade beta-reading responsibilities. (This is far from a rare opinion; in fact, this special case has its own name, critique partners.) Failing that, bookworms at least know enough from experience about what they like or dislike to tell you where your WIP "doesn't feel like a real book yet".
But if you don't even know people who like consuming your chosen medium - novels, in my case - that leaves what I'll call non-readers. (This isn't meant as judgemental, because everyone has different media and genres of interest, and whatever you write there's such a thing as the "non-readers" that go with it.) And yes, I'm aware one can meet new readers and writers online, but this question concerns whether non-readers are also a valuable resource. It would be a shame if they're not, because every WIP needs several beta readers.
I've not personally had much luck meeting new potential beta readers online, or even at writing conferences, and this has turned my attention to friends or friends' friends. Among them, an interest in reading is hard to come by. I recently persuaded one to read quite a large body of my work, but I subsequently learned I had misunderstood their circumstances, and that they're not the bookworm I imagined, but instead a non-reader.
Although the feedback is in its early stages, it seems to often have unusual expectations for how novels would be structured, and the things they like or dislike and the reasons why are at odds not merely with the views of my previous beta readers, but also with what we're usually told readers look for. Of course, a non-reader may judge a medium with which they're unfamiliar by criteria more appropriate for what they normally consume.
Therefore, part of me feels I should take any critical feedback in their notes with a pinch of salt. To an extent, I could do that even if they were a bookworm; writers are sometimes advised to accept opinions two people agree on, be it themselves and one reader or two readers but not themselves. However, I worry that that takes too narrow a view of what advice to accept if one has only found a very small number of beta readers.
And another part of me feels that any excuse not to take someone's views too seriously, no matter how "logical" that excuse may be, paves the road to declaring one's writing already polished. I absolutely don't want to be close-minded; but I wonder whether non-readers' advice does more harm than good.
I'd planned on titling this question something like, "How can non-readers be useful beta readers?" I was advised this was so subjective it would likely be closed, so feel free to answer whichever question you prefer. And feel free to offer any mix of standardised advice and your personal experience. I'm sure I'm not the only person here who's tried getting feedback from non-readers, or light readers or whatever we call them. Can it work? Are there dos and don'ts, beyond what normally applies to getting feedback?