I don't want to oversimplify the issue, but a game like Hearthstone seemed to be in a different situation comparatively.
On the one hand, I seem to remember that game doing a decent job easing you in with tutorials. I was familiar with TCGs, so it didn't matter to me, but I thought it was decent at the time. And on the other hand, a game like Heartstone had the advantage of being a solo experience. Suck? No problem, only matters to you!
I don't know if Blizzard just didn't account for it, but if players suck here, you can drag down multiple people's experience. It sounds basic to say, but it's a factor.