They were on far, far worse teams with terrible GMs.
Buffalo fans knew any chance of building a contender went out the window when Botts traded O'Reilly. Eichel then got pissy because...why wouldn't he? He was on trash teams that were poorly coached for his entire career. Reinhart they screwed the pooch on by not locking him up long-term. They were good players surrounded by bad mentors, mediocre teammates, and, worst of all, they had GMs who were ass at their jobs. Pegula also appears (or appeared) to be too involved.
That's what it takes to have the longest playoff drought in the league, so no, the Sabres are (and were) always going to be bad- to-average until they find good management.