Regarding the defensive system vs players discussion, I really think fans lean way too heavily into the "Offensive System" excuses.
There are two examples of goals scored against us in the past week that immediately spring to mind.
The first example is GA3 (the GWG) against Edmonton. This is an example of system breakdown. In the first screen shot Dahlin aggressively tries to cut off the neutral zone outlet from Ekholm.
Dahlin misses the puck, and Edmonton immediately has a 2-on-1. Even though Skinner is good position on the backcheck, the defenseman has to concede the blueline, resulting in an uncontested zone entry. Eventually, Foegele finds McDavid coming with speed and the goal is scored.
We can argue about the quality of the goal or Bryson, but this goal is a product of the aggressive system. Dahlin's aggressiveness in the neutral zone starts the entire play.
Now, for the second example, GA3 against the Stars last night. Heiskanen streaks in from the point and finds Benn in front, who lifts the puck over Comrie's shoulder.
On this goal, perhaps the only one playing the "system" is Jokiharju. He attempts to pressure Heiskanen, and gets low to try and deny the pass. He doesn't do a great job with it, but I can take players making mistakes while doing what they should do. The other four Sabres are covering no one and just watching the puck. I mean FFS, Heiskanen could have done anything here - kept skating around the net and hit the backside man, or even went high slot. Every Stars player in this shot is completely unmarked.
There is no system in the world that tells you not to physically engage an opponent standing near you. This GA should be chalked up to youth, inexperience, lack of attention to detail, poor awareness, laziness, you name it. Point is, it's on the players, not the coaches.
From my perspective, an overwhelming majority of goals against have been similar to this one, and the fault is with the players. I honestly think this to be is expected, these are kids, they've never had to play with this much attention to detail their whole lives. At the end of the day they'll figure it out, but I don't have concerns about the system being the problem.