Have to agree here. There are plenty of games where it's fun just to mindlessly murder everything in sight just for the shear fun of the combat. I don't see why you couldn't put an RPG into that kind of gameplay setup. Warframe was this for the longest time, you'd just keep playing it because it was fun to slaughter Grinner by the thousands and the RPG mechanics were there to help you decide how you wanted to go about doing just that.
Lots of ARPG's get away with a very minimalist story to begin with, and it's mostly there to lead you from one place to the next and give a sense of consistency rather than to be engaging by itself.
The elephant in the room is if anyone would buy an RPG without a story. I'd say probably no, since the story is usually the main attraction of the genre for most. Remove it and you're going to alienate a lot of the core playerbase.