You're on an island.
When Manning retired, only Unitas, JBrown and Favre had 3 NFL MVPs.
Nobody had 4.
Manning had 5.
That is, in 5 of his 16 years, he was the Most Valuable Player (GOAT) in the league.
An untouchable record.
Brady got 3rd AFTER Manning retired.
And it's accentuated by 7 times All-Pro.
That is, in 7 of his 16 years, he was the Greatest QB in the league.
Unitas and Luckman had 5.
Brady got 3rd AFTER Manning retired.
7 is untouchable too.
If much of the Pats success was attributable to Brady, he'd have more than only 3 of each.
The lack of more tells you what everyone knows: he's a good QB on a great team but not in Manning's class.