When people don't read the article, they tend to do one of two things - comment on the title (which is often misleading) or use the title as a springboard for politically-driven polemic. Both drive down the quality of discussion considerably. The fewer people who read the article there are, the less substantive the discussion becomes, less insightful, less novel, more tedious and repetitive. The best comments are, invariably, informed by the content of a well-written, insightful article.
The goal of this community is to gratify intellectual curiosity. If most people the forum and never engage with the posted content, preferring only to engage with other, similarly unenlightened commenters, how is that curiosity ever going to be gratified?
It's as if Hacker News were a book club and you said it wasn't that important to actually read the books. Yes, it's possible to discuss A Confederacy of Dunces by only having read the cover and back blurb and hoping someone else in the group actually did the legwork, but why join a book club in the first place if you care so little about reading?
Unfortunately, I think your other points are correct. It isn't possible or even feasible to force people to read the articles. More people have to want to put in the effort and if they don't, they don't. There should at least be as much social pressure within the community to expect people to engage with content as there is to suppress humor or incivility, but the insularity and elitism of the culture here makes that infeasible. There's no way to engineer this, people have to care more.