The Steelers lost an All-Pro wide receiver in Antonio Brown, and Big Ben is partially responsible. Roethlisberger's attitude was a problem last year, and he was called out by former Steelers players for not talking to teammates one-on-one while being critical of them in public.
If you're calling out people in the media, there is no way anyone in the locker room will trust you. There is even a report of Roethlisberger fumbling a ball on purpose to protest a play called by offensive coordinator Todd Haley. Putting your team in a bad position for a petty disagreement is next-level terrible.
There is no way a player can lead a team to two Super Bowls and be considered a bad teammate. Roethlisberger knows how to push people's buttons so they play their best. Roethlisberger's strategies might rub people the wrong way, but that doesn't make him bad.
Respected Steelers vets like Maurkice Pouncey and Ramon Foster have defended Roethlisberger's leadership and what it brings to the organization. Teammates calling him out after they've left the team is weak.
When you've won as much as Roethlisberger has, there is no such thing as being a bad teammate.