The Bucs are instantly better bc they don’t have a guy at QB who will turn it over 35x this year. You keep glossing over that anarchy. Even if Brady is just average the team should be better.
I get what you are suggesting, but there are a lot of components to this that are far from a given. For starters, most people are taking the position that Brady is healthy, plays better with better weapons, and gets a full 16-game season in with decent Brady-level production from earlier in his career.
I already outlined how poor Brady's numbers were last year. They were better than Peyton's numbers from his last season, but not by a ton (Manning had a better YPA but with a bunch more interceptions).
Yes, in theory, if Brady's skills were not a problem AND he stays healthy AND he clicks with his new teammate AND they get a full offseason of practice in, then Tampa could be a lot better. However, Brady is in unchartered territory. Only one QB that was 43 years old has thrown even 100 passes in a season (Vinny Testaverde with 172 attempts).
Brady is a stickler in having his guys see what he sees and then running the right routes. I don't know what system Arians uses, but NE requires receivers to run hot routes. Depending upon the defense on any given play, guys will have essentially three or four layers on every play of "IF this, THEN that" as potential outcomes. There are the initial routes based on what is shown pre-snap. Then what the coverage is as the ball is snapped. Then if defenders rotate or move at the second level, third level, etc. It's very complicated.
That was part of the issue last year Brady had in working with new and different players. He expected them to cut at a certain point and they didn't. That contributed to drives that stalled, some interceptions, pick sixes, etc. He also at times got frustrated and just threw the ball away (many times with lesser known guys open but he didn't look their way).
Brady got to the point where he didn't trust his receivers. He even got in shouting matches with Edelman because he turned the wrong way or cut his route off at a different spot than Brady was expecting. The point being, there is no way of knowing how Brady will do with an entirely different cast of characters with completely different coaches. If a play is called that initially is for a 12 yard out pattern but should be cut to 6 yards, the receiver could run 12 yards, Brady throws the ball for 6 yards, the DB picks it off instead, and then like Winston it's off to the races the other way. None of us know if that will happen. The odds are good it will happen less with Brady, but the odds are also pretty good that it will happen more than it did in NE.
We've seen the best case scenarios as I just mentioned (Brady does better, stays healthy, everything clicks, and TB goes to the SB). But it is not completely out of line to wonder what happens in the early going if things don't click, Brady looks like an old man, Brady does turn the ball over a few times, the offense is stagnant to start the season, and then Brady gets hurt and misses a ton of time because he can't heal up right. By all accounts, he was hurt a lot last year but insisted on playing through it. Any outcome is on the table. Tampa could start 1-3 and Brady gets hurt and is out 4-6 weeks. Then what?
The other thing lost in this is the what could have happened if Winston came back, made some better decisions, cut his turnovers in half, and then the Tampa situation could have been dramatically different even without Brady. Earlier in his career, Winston's interception rate was 2.5-3.2%. Last year it shot up to 4.8%. His TD% has generally increased over his career. We'll never know because it won't happen. But with better coaching, if Winston just cut down on his interceptions, he would have been worth the money they gave Brady and then some.
BB knows it is extremely difficult to rely on a 43 year old QB. I am sure NE ran the potential projected numbers (high side, low side, most likely outcome) and didn't like what they saw. The Raiders were said to be in on Brady until Gruden watched actual game tape from the past two seasons and determined Brady wasn't worth the money and backed out of the running. Long story long, there is a lot of risk with Brady (and it's not just coming from me). Like I said, we won't know for quite a while how this will play out.