The reality is accomplishment is used in GOAT conversations and rightfully so. Look at MJ for example, there were definitely better all around basketball players throughout the years but six rings is huge, even if he never really got it done as the lone great player on a team. And the argument against LeBron is always the lack of rings in an era where his path to the Finals was comparatively easy. There's an eye test too, but accomplishment comes into the conversation.
With seven rings and doing it with two teams Brady can be called the GOAT and there won't be that many people that argue otherwise. He passes the eye test as a great football player and fantastic mind for the game. That, combined with the accomplishments, makes his argument an easy one. Is he the best quarterback to ever play? No, and I don't think it's particularly close. But he's won seven rings playing the most important individual position in possibly all of team sports. Can't be ignored.