People are probably unimpressed by Overwatch because even though Blizzard is making
some progress, it's been rather slim.
All the female characters on the poster have the same body type (compare to the great variety of body types on the males), which is of course the idealized conventionally attractive type, and most of them are still sexualized for no reason, just not on the same level as they used to. It's like they can't help themselves.
[Edit: it's weird how Zarya, the one female character who does have a different body type... isn't on the poster. GG Blizzard]
[Edit 2: oh they added her later... after listening to critics! How about that, critics having an influence. Damn SJWs censoring... oh wait xD]