Also people seem to forget that every team builds around its players strength. The Peyton QB'ed colts were built around scoring points, so they invested in that side of that ball. The Bears know they cannot score 20 points on a good day so they invest heavily on the D. The patriotsbuilt a team with a strong line but crappy offense skill position players. There is no single blueprint on how to build a team. You have to build around your strengths.
Cam's strength was moving in and out of the pocket, so that made having elite tackles less of a priority because Cam was able to mitigate that... Which then lead to the team being able to invest in other positions. Its all give and take.
Its lazy to blame the demise of Cam on a single position group.