That depends on what your measure of success is.
I don't know if any sports fan is content with their team, regardless of the sport, that looks great every season but flops and/or chokes in the playoffs. Playoff success is the bar for success.
And when the home team loses 6 consecutive playoff rounds, 3 of the last 4 when they had a 3-2 (or better lead) and the last 3 all against lower-seeded teams, something is clearly wrong and needs to be fixed. If Dubas can't put together a roster capable of winning at bare minimum a single round against a lower-seeded team, the overwhelming majority of fans, sports writers and analysts would agree a change needs to be made.
I'm not sure how that logic is "horrifically flawed."
So you’re upset over last years playoff series? Where they were one arguable waived goal off from advancing? Against the back to back Stanley cup champions? A simple case of two great teams where only one could advance?
Or are you upset over the two bubble seasons where in one of the years saw the playoff series played months after the season ended, and overall saw teams that shouldn’t have been in the playoffs advancing.
Or are we judging this team based on results from 4 years ago when the team wasn’t even close to what it is now? In many regards?
Or are we blaming Dubas for the two seasons before that when he was only AGM?
It’s incredibly flawed logic to let go of a GM who has shown to be a high quality GM, based on two highly irregular playoff formats, and a highly competitive well played series against another top team in the league (arguably top at the time) that just happened to be in round 1 due to playoff format.
It’s an irrational, purely emotional decision and ignoring all context and variables.