Minecraft was very fun and was selling like hotcakes when it had "no tutorial to speak of, no on-ramps for new players". Even nowadays there's no tutorial as far as I know and much of how to play is left to discovery. The achievements tree is a bit of a guide, just by telling you some of the things that are possible, but it sure doesn't tell you how to do anything.

I think having an official tutorial or an on-ramp for new players is not a requirement for a good game. In a broader sense of the word "game", a game is separate from a tutorial, so a good game can exist without a tutorial. Chess has no official tutorial or on ramp for new players, and yet it's widely considered to be one of the greatest games.