Personally, a lot of the enjoyment I get from this game is seeing new or remixed mechanics or fights I've never seen before and the spectacle of a boss whipping out some super power move I've never seen before.

The requirement to watch a guide, and spoil the entire fight to join most PF parties for any Extreme or Savage content is a huge turn off. Still though, even when I do make a PF specifically for a blind run, I still occasionally get people who feel the need to explain the entire fight in great detail, even mechanics the party hasn't seen, when no one else has asked for it.
I don't think I would ever block because of it, but I might be annoyed and vote abandon.

If I'm joining the DF for new content though? Its hard to say. I've so far been lucky enough to not experience this but I don't doubt that if it happened to me I would feel like the person explaining mechanics was sapping a lot of the fun away from me, well intentioned or not.

Still, the content isn't even 24 Hours old, and if that is too old to be considered for blind runs, I guess I just genuinely don't understand what others find enjoyable about this game.