6-6 in the NFL nowadays is not decent. The league is filled with parity and roughly .500 ball is right where almost the whole league is.
There are always a few terrible teams with 0-3 wins, let's say, and a few really goods ones that go 13-3, 14-2, maybe 12-4.
Then there is almost the whole league around .500.
It's not decent. You need to be better than that to make the playoffs, usually, in most divisions.