The NFL is continuously changing on and off the field. We can see how the running back position is evolving but quarterbacks have also undergone a shift. There are increasing numbers of duel-threat QBs in the game now, from Josh Allen to Justin Fields (via SBNation).
It’s rare for franchises to stick with a pure passer like Mac Jones in the modern era. This shows that Belichick opted not to evolve and reverted to type after Cam Newton departed. Jones was always a controversial choice but Belichick never doubted the former Alabama player because of his playing style.