If you want the shake the culture and bring in some sort of mentality change, I think it's going to take the combination of a significant player shake up and some sort of coaching change.
Addressing the second point first, that could be replacing Granato (unlikely) or simply changing his assistants, who everyone roundly things are not very good. Many of us having been posting this point since early in the season when the PP was bad.
For the first point, I still think a trade for Brady Tkachuk would be a hard trade to make but easiest to fix the Sabres. He's a warrior who drags his team into the fight, and as a player, does most of the things the Sabres do not want to do.
I'd move Peterka, Kulich, Jokiharju and the 2024 1st, unprotected. If they asked for Levi, since their goaltending sucks, I'd strongly consider switching out the 2024 1st with Levi.