Certainly there are examples of people who failed once and then succeeded greatly (including two of the best coaches in the league), and somehow Rich Kotite got hired a second time, but yeah, I think the NFL is probably less forgiving than the other sports, a couple of 6-10 seasons is a real drag on the resume whereas a bad run in the other sports still might be .500 and the odd low-end playoff berth.
Anyway, back to Sixers. Despite the finish I would still say any team that starts with the three guys we start with, and even Richardson for now, can be Top 4 in talent, even including the Nets. They just haven't had the cap space or acumen to build the right team around that talent. And, including Harris, it will always be too top-heavy if Ben and Joel don't truly emerge as Top 3 to Top 5 players in the league, rather than Top 10-15.
You can say Joel faililng to make NBA was a positional quirk - he had to be one of three rather than one of six - but of course he's been second-team before.
And we still have whole 'nother problem, which is that we're just trying to be good enough to win the East and last year might have been the only time the East wins it all again for while. If Brown had done better he might have still gotten fired for failling short of the ring.
Amazingly, until Toronto, Doc Rivers was the last coach to win an NBA championship in the East without LeBron, and except for David Blatt's year Lue and Spoelstra are also the only coaches to appear in them out of the East (again until Toronto, but now the Heat are back this year).