Top of the list, I think, is… just some old-school D&D. Technically, probably Old-Shool Essentials or Dolmenwood, both of which are retroclones of B/X D&D.
I just got into watching Dungeon Meshi and playing Caves of Qud, both of which are just dripping with old-school D&D influence. Plus I’ve never actually ran a full dungeon or hex crawl.
Honorable mention to Burning Wheel, 16-time annual winner of My Favorite Game I’ve Never Played. :P
I’m not sure if they deleted it or I just can’t find it, but there was a post on the LW destination that said the mods talked about the near-universal, overwhelmingly negative response, and were split 2-2 on what to do: either cancel the plans, or keep going anyway. They only made this post after considering the aforementioned near-universal, overwhelmingly response a tiebreaker.
I think that really encapsulates the problem.