Am I in the minority here in thinking that at least the anniversary type posts are really not that bad?
Yes.
I have seen it done elsewhere in a similar fashion for milestones...
Why is what's done "elsewhere" relevant here?
...and even done here I think long ago before more recently.
See my previous point--when it was once in a while and led to interesting threads, it was one thing. But it's gotten out of hand lately, and more often than not seems to lead to junk threads. So, what was done "before more recently" is irrelevant--it's what's happening
now that matters.
As clickbait goes, I feel like there's much worse honestly than these.
Again--we're not talking about use of clickbait anywhere else. We're talking about it here.
Although, I suppose if you wanted to keep that theme around as I feel there is some merit to the concept, what you could do is open up a day in history thread similar to the obits. Might become a little redundant at times maybe, but it'd be a thought.
No, what you do is make your users title their threads appropriately (example: "GREED's 20th Anniversary" for the thread in question). That takes care of the problem from every direction--it makes users think before they post; it doesn't waste everyone else's time opening thread after ambiguously-titled thread to find out what they're about; and it discourages posting of redundant threads (no more "I don't know if this was posted already" because you already saw the clear titles of existing threads, and know full well whether you're being redundant).
Basically, anything that forces people to think before they post is (to borrow CU's term) a Good Thing.