Grouping is already required for the MSQ. It always has been. We've always been required to do dungeons and trials. And yeah, for some, that's gonna suck. I have a good friend who quit months ago because of it. I myself got irritated at times because the queues were long and some of the dungeons themselves, frankly, sucked.
I wouldn't be opposed to there being a solo story version, but I'm guessing that's a whole lot more dev time than they're evidently willing to put in for this. The easy solution on their end is to just require the content that already exists.