It was a totally different era. Can't compare QB ratings and what not to modern-day players.
That said, stats-wise, Archie was not elite in his era. But that's looking at the numbers in a vacuum. The New Orleans Saints under then-owner John Mecom were comparable to the NBA's Clippers under Donald Sterling. Mecom, the playboy son of an oil-rich family, didn't care even a little bit about winning. Imcompetence was installed in the Saints front office from Day One, as being Mecom's buddy was more important than football acumen. Under this mismanagement, the Saints suffered through 15 seasons of abysmal drafting (not rectified until 1981 under Bum Phillips).
Back then, with no free agency, if your team kept drafting poorly, the hole dug kept getting deeper. There wasn't parity and annual turnover in the standings like there is now.
Despite all this, the Saints did put up high-flying offenses in the 1978 and 1979 seasons. That was the clearest window into what Archie's career might have looked like on a contender.
This is only anecdotal, but I recall an article in Football Digest, sometime around 1983-1985, where Archie was compared to Staubach, Stabler, and Griese. The consensus of the writers, players, and football insiders interviewed for the piece was that Archie had the physical tools and the acumen to have been a HOF-level player for Pittsburgh, Miami, Dallas, Los Angeles, Oakland, etc.