I think you are over-simplifying. Flyers have been to the Cup finals 6 times since winning their two Cups: 1976, 1980, 1985, 1987, 1997 and 2010. Fred Shero, Pat Quinn and Mike Keenan are all legendary coaches and rightfully so. Shero got the Flyers to the finals 3 straight years, winning 2. Keenan got the Flyers to the finals twice in 3 years. Murray and Lavs were not legends, but very good coaches.
They ran into dynasty teams in the finals every time: MTL in 1976, NYI in 1980, EDM in 1985 & 87, DET in 1997 and CHI in 2010. The Flyers were plenty good enough to win those Cups, but dynasties are just that for a reason. They beat everyone for sizable stretches (MTL 4 straight Cups, NYI 4 straight Cups, EDM 4 straight Cups, DET 3 out of 4 Cups and CHI 3 Cups in 6 years).
The 76ers, OTOH, I agree more with your analysis. They also ran into a dynasty in 2001, but I think everyone knew that was a special season that would not be duplicated due to organizational, coaching and personnel factors. Plus they had not sniffed the finals since 1983 before that and certainly not since then. It has been a poorly run organization for decades now spanning several owners, many GMs and all kinds of coaches and players.
I agree the ownership and management are critically important which is why I've been advocating that Brand be replaced by a much better GM with full authority over basketball operations. I'm hoping Harris sells the 76ers soon as he only bought them as an investment and does not seem to truly care about championships or building a consistent winner. I agree the 76ers gig may be viewed as less interesting by coaches who'd like to work for a good organization.