As a 500hr+ Overwatch player and 1000hr+ TF2 plater, I also thought this at first. While Overwatch was certainly heavily inspired by TF2, it plays considerably differently. Overwatch has six players per team each playing one of 32 different unique heroes. TF2 has 12 players playing one of 9 classes. The abilities feel much more impactful in Overwatch. TF2 was all about supporting your engineer and racing for Uber, while Overwatch is much more about positioning and mechanics (though ult economy matters too). Removing the ammo mechanic entirely was brilliant IMO as well. Anyway, just a few cents from someone who has played a lot of both of those games.
