that is why I don't take many of the advanced stats seriously. The advanced stats exist in a vacuum, not reflecting the reality of the situation
It's not possible for a stat to account for shooting talent, goalie talent, the volatility of either and the pure luck involved in both on any given shot. xGF% is essentially the stat that measures what is left over once you remove all of those factors. It's a stat to measure how well a team is playing if you ignore the actual scoreboard.
It's shots for + a model that assigns a value to each shot based on the distance and angle to the net. It's a lot less complicated and lot less predictive than most people think it is.
xGF% does a great job at measuring how well a team is coached, how successful they are at running their system, and how hard they work.
Carolina dominates xGF% every season. They are well coached, they execute their system well, they don't tolerate lazy players. They aren't the most talented team, but they come to grind at 100% effort every game, all season long and that's why they've been in the playoffs for 7 straight years. Which is every year that Rod has been their coach. They consistently score well below their xGF because they don't have the talent. It's more indicative of their system and coaching, than the talent, but it also wins them a lot of games. Every second they spend grinding in the offensive zone is a second they aren't playing defense.
And then you have the Sabres. One of the most talented teams in the league when you look at each individual players raw ability. But we've consistently been bottom 8 or worse in xGF% over the course of the drought. Bad coaching, poor execution of the system, and lots of lazy disinterested play. We have the ability to outscore our xGF by wide margin as we have a ton of shooting talent. But it's nearly impossible to sustain success when playing as poorly as we do.
And when our key players are out injured or playing through injury, it evens out our shooting talent closer to an average team, and we have nothing to fall back on aside from our piss poor system and execution. It's not a surprise we have such large losing stretches every season.