Guys like Hoffman, Granlund, and Zadina just aren't good enough. Hoffman would have been retired if he didn't have this last year on his contract, Granlund was a total flop buoyed by Josi on the power play, and Zadina is a busted prospect who doesn't actually have any NHL-average skills. You could keep applying this to the rest of the team - Vlasic is done for, Kahkonen is not an NHL goaltender and just looked good on Minnesota, Rutta's a 7D, Duclair is a mediocre middle-six scoring forward coming off an injury, Smith is a plug, etc.
Effort isn't their problem - skill is. They're just not good enough.