The misnomer about the Falcons passing attack under Mike Mularkey was that it was a run-based attack, or the Falcons didn't throw alot. On the contrary, if I'm not mistaken, the only QB whose has more attempts than Ryan the past two seasons is Brees.
But the Falcons offense was largely built around the concept of securing first downs in a 10 yards at a time way. There was probably no better team in the NFL at putting together long sustained drives than the Falcons over the past 2-3 seasons. It really was the benchmark of their offense. But against better teams, that can cause issues because 1) better defense can do a better job at stopping long sustained drives and 2) if you fall behind, you may need to strike more quickly. The Falcons started to show a more explsive component in the second half of last season against inferior competition as Julio Jones got his sealegs and Ryan's trust in him grew. But ultimately, the personnel on the Falcons had changed to a group that probably wasn;t the best fit for what Mularkey offenses look like.
So if Ryan's YPA is in the low 7 range, the Falcons have a real problem because IMO, Koetter was brought on board to meld the offensive weaponry the Falcons have with a scheme that puts them in a position for better YAC opportunities. The screen game has been largely absent from the Falcons offense the last 4 years and this is an area where many fell Koetter will lean on Jacquizz Rodgers to become a prominent offensive force. But ultimately, I think the change in mindset from becoming a first down offense to one which looks to maximize its talent and put that talent in a position to make big plays more consistently is what the Falcons were looking for.
Can Koetter cut it? I think his track record was sullied for sure in Jacksonville but it's undeniable he had little to work with other than MJD the last 2-3 years. But more than that, I think the next step in Ryan's career is for the offense to be his, where in a sense he starts acting like his own OC. It's long been thought he has the smarts to do this, but under Mularkey, you'd only see it in spurts, largely in the no-huddle. This is something Koetter is promising more of and if Ryan's influence and command of the offense increases, Koetter may become more of a Tom Moore type OC.
Lastly, after Ryan's rookie year, IMO he all of a sudden became drastically overrated in fantasy. He was garnering Top 12 mention with a promising but hardly prolific rookie year under his belt. 3 years later...I almost think he's being underrated. His stats are thisclose to being in that elite 4500/32 tier and there exists upside beyond that. Is his arm like Stafford's? No? Are his legs like Cam's? No. But we are talking about a player who has a career 43-19 record...you don't get that by accident and aside from a shaky second season, is a great decision maker. I had thought that he stopped taking risks after his rookie year and perhaps that's taken the edge off his game some. But I think the perception of his talent is now underrated and he could make a big jump.