If a questioner provides thirty details of a forgotten novel, it should not be necessary to address each and every one, is it?
Nobody said that it was necessary. When no matching details are offered, I (and some others) tend to encourage the addition - but only in order to make the answer more useful. I, at least (I can't speak for anyone else) never flag an answer without matching details listed for deletion because they're not invalid answers, just less than optimally helpful.
Plus, there is so much detail provided in some answers that going on to read the story is superfluous.
Well, that largely depends on the purpose of the identification question. You assume the person is looking to reread/rewatch it themselves. While that's probably the most frequent reason, they could just as well be wanting to find it for someone else.
But this is why I (again, can't speak for anyone else) find it best only to describe matched details. If it's something that the OP already vaguely remembered, it's not a spoiler. But if you are concerned about giving away too much, or about paraphrasing too much of the story, go ahead and throw some of the answer behind a spoiler tag. They may not always be necessary, but the courtesy is never a bad thing.
The problem with just offering blurbs or rough synopsis of works is that when it comes to sci-fi, there are so many stories that have similar premises. Go too vague, and you don't necessarily offer enough to confirm the match. Go too specific, and you risk spoiling the story. Find your middle ground.