Problem being, Buffalo didn't have assets handed to them on a silver platter to parlay into trade collateral, instantly making them competitive in a player-friendly market. Fans here constantly and stubbornly ignore the fact that no matter how nice locals know the area is, players and coaches who don't know are not wanting to go there. Stastny and Stone never consider signing/extending in Buffalo, and no GM can change the perception that Buffalo is a boring nowhere-land. We can rely on Ontario natives being close to Buffalo and Pegula handing big contracts out, which has happened a few times.
In before, "But if the team were good everyone would come" response. That works if you actually believe players and coaches care about only hockey. What big name UFAs signed in Buffalo ten years ago? Ehrhoff is the only guy in his prime.
So if you're looking for best cynical post of the day, I'll see your "The GM is no good" and raise you "The area is not attractive and no GM can change that".