People can bitch about them signing Haskins, but there's virtually no risk to the Steelers. They've got nothing invested in him and if he can get his shit together, he could end up being a really good NFL qb. If he continues to make bad decisions, the Steelers will let him go and lose nothing.
As for Bell & Brown - They tried to keep LeVeon, but he chose to go elsewhere. He turned down more money (offered by Pittsburgh) than he's made in NY and now KC. Can't say the Steelers treated him poorly. Brown turned into an ego-maniac clown who was bring way too much negative headlines to the Steelers. At least they got something for him, unlike Oakland and New England (Brown's next two landing spots).
The me-first attitude in the lockerroom is a problem and needs to be addressed. Their list of unrestricted free agents is massive (JuJu, Conner, Villanueva, Dupree, Alualu, Sutton, Hilton, Feiler, Banner, Berry, Wormley, Dangerfield, S. Davis, Dobbs, Marsh). Depending on which of these they attempt to retain, it will tell you pretty quickly if they're trying to repair the culture in the lockerroom or not.
Vance McDonald has already announced his retirement and reportedly Pouncey won't be far behind. Ben's got - at most - 1 season left. His contract runs out after the 2021 season, so things will be looking mighty different in Pittsburgh over the next year or two.