Belichick does deserve some credit for helping the 199th pick in the draft become the G.O.A.T., and helping him get to 12 AFC title games and 8 Super Bowls.
But I'll go with your idea to look at Belichick without Brady:
Belichick spent 12 years with the Giants. The last 6 as DC, in which the Giants won 2 Super Bowls.
After winning his second Super Bowl, he was hired as Head Coach of the 3-13 Browns. They won 6, 7, 7, and 11 games, winning one playoff game in his 4th year. Then the 1995 team disintegrated as a lame duck team that planned to move to Baltimore.
1996 as a New England assistant, they go to the Super Bowl but lose.
Then the weirdness went down with the New York Jets, where he did manage to squeeze in an AFC title game appearance.
He was then named New England head coach. I guess we only look at the year that Brady was hurt, and Belichick helped Matt Cassel go 11-5.
So, without Brady:
3 Super Bowls
2 Super Bowl wins
1 AFC Title game
With Brady:
12 AFC Title games
8 Super Bowls
5 Super Bowl wins, so far
Overall:
16 conference title games
11 Super Bowls
7 Super Bowl wins
His coaching resume without Brady is better than most of the guys who have ever coached in the league.
His coaching resume overall is easily the best of all time.