I'm surprised plus/minus is still being used as a main statistic, as flawed as it's proven to be.
I think it is a stat with many flaws and people who have looked at it much more closely tend to really think so.
Having said that, to me the question is why is points and goals per season or per game seen as such great end all be all stat in practice? If you say it ain’t so, go to any discussion about best all time, Hall of Fame worthiness, player x vs player y, and you will find page after page of points and goals stats without that much nuance. The belief in points as a really great overall summary stat is so strong among some that they even think era adjustment is bad - it’s points and goals and not much else.
Hockey games are won by scoring more goals than you let in and the latter aspect has so much less weight in virtually any discussion.
So, circling back to topic, +/- seems to be very flawed, but then what do you do?
BTW, just yesterday Matthews is beaten defensively for Dallas to score, then scores with a beautiful shot a few minutes later. Only the latter will count in discussions about his greatness in the future. “He was not good defensively” will be countered with “No he wasn’t’” or just ignored and that’s that. (I don’t watch enough Leads to know if he is great ok or bad defensively - it’s just an illustration of my point)