Kingdom Death: Monster is the example of a campaign failure state that I’ve played, and it ended every group’s interest that I got to start a campaign. Seeing new things was all good. Being told to replay the 40 or 80 hours already invested was too much overhead to getting back to the discovery.
Probably if the early game play continues to feel fresh, or is greatly accelerated, failure->restart isn’t as bad. I stopped Darkest Dungeon after getting to the final set of bosses and realizing I would have to sacrifice a team to each one to learn its trick, then regrind everything to face the next one. (I.e., I’m not good enough to beat bosses on seeing them the first time.) I hear later patches addressed some of that reset-to-zero aspect.
The first scenarios in Gloomhaven the group of four I’m playing with failed it three times, and then failed the next couple a time or two each. I was worried we were going to hit a soft failure state, where levelling up from fail XP without getting other rewards would actually advance the monsters more than us. But, the last two scenarios went much better. Having the game indicate that we’re learning to be better at it is a great feeling.