Yep. No doubt. We have developed a clear pattern of moving the ball well until we get to the red zone. Then we become a totally different team (head coach down to where the rubber hits the road).
I remember a few years ago, the 8-8 years, when we struggled in the red zone. It cleared up when we started to fix the O-line first with Tyron then Frederick and added Murray. That's why I don't put much stock in missing Dez and Witten. They were both here during those years and we still struggled until we drafted for the O-line. Now that O-line is an egg shell of what it was.
Yes it goes to coaching somewhat because some seem to make do with average but there aren't many coaches who can sustain that. Bellichik has won a number of SB's with average except for the GOAT and Gronk. He and his coaches around him seemed to be able to coach average skill up to above average. Look at the Pats this year with some of the coaches leaving though. So yes, coaching is a factor, that and the age of the GOAT and the wounds of the Gronk. Richard has done a nice job with our D BUT give him 60% backups on the line or in the secondary and we would probably call for his head.
IMO if the 2018 O-line was the 2014, 2015, 2016 line we would have fewer problems in the red zone. Of course that's impossible to prove just as saying a new OC or HC would change our red zone woes. Hey, if we end up 8-8 we could see some changes in both. 9-7? Your guess is as good as mine