Google Cardboard is pretty bad, but then that's rather the point of it. It's "minimum viable product" taken to an extreme: how cheap can you make VR and still have it be somewhat interesting. Google cardboard demonstrated that you can make VR incredibly cheaply and still have it be an eye-opening experience. Of course you don't use cardboard for hours on end, I'd be surprised if anyone used it for more than a couple minutes on-end. It's still a great introduction to VR though since it definitely demonstrates the potential of vr for nearly no cost.

If not for google cardboard I'd never have invested in a vive, and probably written the whole thing off as a gimmick.