Yeah, it seems like pretty good circumstances to miss Brady for 4 games. Beginning the year, 3 at home, and the only "good" team is Arizona who finished their season crapping the bed last year... Plus, as you said, Jimmy has another year's experience in the system. It could be so, so much worse.
It begs an interesting question: Would you rather be without Brady 4 games with Jimmy G and BB leading the team, or without BB for 4 games with Brady and McDaniels leading the team? I think BB is the more important piece in that sort of circumstance, with all due respect to the GOAT QB of course.