Well yes an entirely alternative landscape popped up in the 90s. It was even called “alternative “ at the time. You also got Americana (alt country) during the same period. I guess I see it as a sea change of the time in music in general as opposed to grunge being some sort of linchpin.
But grunge is what triggered that sea change in the mainstream (and again, not a fan of grunge at all but I think credit where credit is due)