I've stated previously that I think the definitive Broncos culture was lost back around 08 when Petero was let go.
Around that time we lost Petero, Webke, Carrol, Thorn, Tate, Berro, etc. Basically the only remnants were Lockyer, Parker and Hodgo. Khunt also moved on and I'd say if he stayed he would be our current captain and 5/8.
It was basically the first iteration of adopting a youth first policy as McGuire, Macca, Norman, Beale, etc. came in to fill the voids. The major issue being that all the old heads had moved on before imparting the Broncos culture onto the youngins, which would create an ongoing cycle of the old culture for striving to succeed rather than making up the numbers.
Soon enough Griffin moved into the head coaching role and you could say at that point it was basically up to the 08 generation to create their own culture, which is where I believe we are now.
Basically I'm blaming the current culture of the club on Bruno Cullen who appeared to be the architect of the youth first policy version 1 and Anthony Griffin who allowed and nurtured the 08 generation to create the current culture we see today