As a Packers fan, one common complaint about McCarthy was game management. And even thinking about that last play at that point was a bad idea. Drew Brees said during the pregame of the Chiefs/Steelers game, you need about 20 seconds to pull that off. It did look like they practiced it though, but did not account for the official having to place the ball. That mistake is a coaching error. Penalties killed the Cowboys too.
So the extra playoff team and extra game combination may have may for some crazy scenarios at the end of the regular season, the play of the two 7 seeds showed that in football, unlike most other sports, a larger playoff field is not a good thing.