I don't know, nonsensical premises have existed in the past and it could still be fun. But for RPGs, I still at least would like a sensical story because a game with a great story but incredibly boring gameplay will just make me too bored to want to continue. Especially games with forced grinding to get to the next point.
In my personal opinion, it should be balanced:
60% fun
40% story
Because if it isn't fun, the average gamer won't last long enough to finish your story. I know a lot of people who gave up on great games just because the gameplay was either too tedious or too difficult.
Story even if not completely original needs to make *sense* at the very least and you need a goal in and direction. Sometimes the most cliched RPG story (save the world!) can be quite fun if told in an interesting way and is fun to go through it.
Uniqueness is needed to set apart your game from all the other games. For example as RPGs, Chrono Trigger and Earthbound are very unique and is set apart from all other RPGs just due to their premise.
One thing I find very important (sorta ties in with the story importance) is attachment to characters or liking them at the very least. Ever played a game where the main character annoys you? How much longer can you play a game like that, even with a decent story and gameplay.
In the end, probably the most important thing a RPG can have and where most fails is the fact... does it give you a reason to complete a game? You need a combination of story, gameplay, character attachment to do so, or else your game will be dropped halfway - or worse, at the start.
There's more to say to this topic but I'll stop here for now