IMO it's the general idea that everything needs to be designed to be duty finder-friendly is what kills any potential of better 4~8 party dungeons.

Just like there are a lot of players who run hardcore content with statics XIV shouldn't have been shying away from designing midcore dungeons for fixed parties. Not every content is supposed to appeal to solo/casuals. It would have been a fun content for people who want more engaging dungeons that aren't routine and don't groan about needing to actually meet players to do it. If they could implement as little as like 2 such dungeons per expansion I would've been satisfied enough.