I think it depends on the thread. If it is someone asking for advice in a very detailed situation that is quite specific to them, it usually seems pretty pointless, especially when the response is clearly aimed at that person specifically. For more general conversations, I think reviving old threads can be great.
It's tough to articulate the difference, but I know it when I see it. That said, it doesn't actually *bother* me. it just seems pointless to post advice about a situation someone posted about, seeking advice, in 2017, and then hasn't been back to update. The details are probably not the same, 6 years later (totally an example, so hopefully this doesn't mimic an actual recent necropost). If it is "should I pay down my mortgage" that becomes pretty general, but if it is much more detailed and personal, it's pretty pointless.