If Belichick had been running the show in Tampa Bay, they wouldn't have the same talent because Belichick has proven he can't draft a decent wide receiver if his life depended on it. Evans, Godwin and Miller were all draft picks. Even Tyler Johnson and Justin Watson look decent. Belichick simply cannot evaluate the position; it's been one bum after another. Belichick also wouldn't sign off on taking shots down the field like Arians. The narrative around Brady for past few seasons was he could no longer throw the deep ball... this season he's one Long Pass Play (>25) behind league leader Mahomes (Brady has 36 completions >25 yards).
Also, how many has-been veteran wide receivers has Belichick brought into camp over the past decade? It's a lengthy list for sure and pretty much none of them have worked out. You have to go all the way back to 2007 as the only season Belichick did anything to surround Brady with a high-powered WR group. Even then, Moss at the time was considered a disgruntled, possibly declining receiver, and we got him on the cheap. Welker was unproven in Miami. Brady only had two seasons with Moss, and the second he was coming back from the torn ACL, even still Moss led the league in TD receptions both seasons (of course setting an NFL record in 2007). Welker had his best seasons with Brady, leading the league in receptions three times. Moss and Welker are the only two pro bowl receivers Brady has ever had and combined he had only seven seasons with them (Moss 2 and Welker 5). By contract Payton Manning had a combined 25 seasons with Wayne (14) and Harrison (11).
Belichick's treatment of Brady over the last few seasons was a travesty. He surrounded Brady with diminishing talent and limited returns which he would then use against Brady in terms of contractual incentives. By the start of the 2019 season, Brady knew it would be his last in New England and he knew the team wasn't good enough anymore (as a result of Belichick's poor roster construction). It's no coincidence the team goes in the toilet the very first season Brady leaves town; just as it's no coincidence that Belichick was 5-13 to start his career in NE without Brady and then 11-3 and winning his first Super Bowl with Brady.
And of course Brady became a better quarterback, with improved skills, as he became more experienced with seasons behind him. Generally that's how it works. He's always been clutch but he was no slouch otherwise earlier in his career. He led the league in TD passes in 2002 and yardage in 2005. He was a pro bowler in 2001, 2004 and 2005. Obviously he wasn't the GOAT after a handful of seasons; he had to build that resume over time. He earned the label after beating Seattle in SB 49; since then he's only piled on considerably. What he's doing now with a new team in Tampa Bay, at age 43, in the midst of all the COVID chaos, is remarkable. By contrast, Belichick has had an utterly dreadful season. He has no quarterback, an otherwise limited roster, has been outcoached repeatedly, even his precious special teams are getting embarrassed, and now the entire team quit on him under a national spotlight.