Penalties are not the issue but they are an issue. We've had ten losing seasons in a row and in that time we've committed the second most penalties and been flagged for the second most penalty yardage (it would take an act of God to knock the Raiduhs off that particular perch).
I looked this up recently, because it just didn't track (in my mind) that playoff bound teams have those kinds of mental mistakes.
Over the last five years, of the 16 most penalized teams, only five have overall winning records. Seattle and Denver stand out the most as teams that win(+ .700 winning percentage) in spite of it.
However, of the 16 least penalized teams since 2012, eleven have winning records. Green Bay, Pittsburgh, Indianapolis, Carolina, New England, Arizona, Kansas City, Cincinnati are in this group.
I went back further for over the last ten seasons and I saw a pronounced difference again. 6 of the 16 most penalized teams since 2007 have compiled overall winning records in that time frame(Dallas, Baltimore, Seattle, Denver), but 12 of the 16 least penalized teams had winning % over .500(New England, Indianapolis, New Orleans, NYG, Pittsburgh, Green Bay).
***************************************************************
Yes, we need to be good enough to overcome penalties but we also have to learn to avoid them. (We were middle of the pack in our GSOT years and also the 1970s division runs). On their own, they may not prevent a good team from being successful but they sure make it harder.