The original generic TLDs have many highly-ranked legitimate sites.

The problem with extended generic TLDs is that the spam sites have managed to become highly ranked. Yes, there's good stuff there, undoubtedly. But search engines can't find it. At which point it may as well not exist.

I'm not a fan of outright blocking at this level without good cause, but it could well be worthwhile to block an entire TLD in cases.

I'll add that if you're getting unwanted ads for that many drug addiction recovery-related terms constantly, perhaps your habits do merit examination.