Chiming in in what others have already said, but I want to say it, too!
Brady has an uncanny ability to make the right decision, which is compounded by his willingness to try an abundance of game plans to beat any given opponent.
Aaron Rodgers might be better on the move, Mahomes might be better at throwing across his body, and Peyton might have had been great at facilitating passing attacks - but Brady can do all of these things to a masterful degree. On top of that, he can do everything those QB's can't, or don't feel comfortable doing, to a masterful degree.
Unparalleled is both his poise and his decisiveness. It's not just displayed in his ability to read defenses, either. Time and time again we saw a QB who knew when to get rid of the ball, who knew how to take a hit and not get injured, who knew when it was really necessary to put his receiver in one of those "over the middle, out to dry" throws that would invariably lead to them getting rocked. He took chances at the most appropriate times, never looking to pad stats. If there was a safer option, or a better option in general, he'd take it.
His ball placement is also astonishing. He could throw it perfectly to a guy like Welker, playing to his small height, placing the ball a touch forward, but also pretty low to put it only where he can get it. He was constantly evaluating how he can adjust his passes to squeeze a few more yards out of a completion. His thought never stopped at the completion itself, but the opportunity for gain after such as well. He can put it perfectly in the basket for those large, tall burners. He had a risk assessment for every single pass, and did everything he could to maximize the return while managing chance for a turnover.
Lastly, and while it's regurgitated over and over again, it really can't be overstated how ****ing good he is under pressure. Even the greats, the top of the line QB's - the literal all-time greats of our sport in this position - had demonstrable tendencies to under perform and get flustered under pressure. It is a universal trait to I'd say 99% of humans. Brady seemed to excel with it, and continually at that. It wasn't just one season, it wasn't just one Superbowl. It was every Superbowl, it was every season.
Dude is a beast. And it still hasn't sunk in that he isn't a Patriot. I love defense, more than offense. But you'll never catch me thinking there's a more important player than Brady. Ever.