Nor was he in 2003.There is too much of “take out the bad games and he’s a great pitcher” in this analysis.
Brady was nowhere near TB12 GOAT when the Pats beat the Rams in what was a coaching masterclass.
His 2003 stats: 317-527 (60.2%), 3,620 yds, 6.9 y/a, 23 td, 12 int, 85.9 rating
Here's where he ranked:
Completion %: #13
Passing Yards: #6
Passing TD: #10
Yds/Att: #12
Passer Rating: #10
Moreover, the team's offense on the whole was #12 in points scored and #17 in yards gained, so it's not like he was leading an elite offense. They happened to have a pretty good (not great, never mind "elite") offense, but had a lights-out defense, ranking #1 in the NFL in points allowed, and #7 in yards allowed.
He was getting better and was moving towards GOAT level, but he wasn't remotely there yet.
So at least the first two Super Bowls BB won with Brady was when Brady had not yet ascended to the all-time great level he would later get to. He was obviously a good quarterback at this point, maybe even a very, very good one. But not all-time great TOM BRADY.
Anyone diminishing Belichick because he had Brady is just spouting nonsense.