Exactly. And those of us who grew up on DC Comics have understood about Earth-1, Earth-2, and umpteen other universes since we were kids back in the sixties. It's not a radical new idea.
Parallel universes aren't a radical idea at all.. to learn about the possibility one must only read about the Multiverse Theory

To be quite frank, the biggest problem I have with the Kelvin and Prime universe, is the Destruction of Romulus.. I could understand the advent of things happening different in Kelvin vs Prime, if it wasn't so attached to a major catastrophic event in the Alpha Quadrant that didn't even need to happen..
But I do suppose they needed a plot device to even introduce one universe to the other.. perhaps I am just grumbling about circumstances rather than the entire situation.