I wouldn't call it "easy." But you and xogfog are talking about two different things. If you're ready to trade either Joel or Ben that's a very different set of options than if you are just trying to get a team to take Horford or Harris. Clearly the success of other teams shows there are ways to win without two (let alone three) stars.
The sky isn't falling, but there's nothing about the franchise that is elite, starting with the owners and GM, so we can only hope they get lucky making future decisions. The whole point of the Process, and the goal for any team, is to have a chance to win championships. That means being one of the four best teams in the league with some consistency. The Sixers have now slipped to the point where they'd settle for being one of the eight best, and might be a lot worse than that (that's what the standings and this year's playoff result says, though I wouldn't read too much into it obviously).
With the two players we have it's not an unsolvable problem, but it's still a big one. A little while back I said the Sixers will never win a title while both Ben and Joel are here and I also said I was being deliberately Negadelphian. But now that seems pretty likely, whether because they can't improve the roster enough around them, they trade one of them, or because of injuries. I see a team that will be like Houston or Portland or Boston (until now?) for the next five years, - always in the playoffs, maybe falling just short of the finals once if they are lucky, but not the class of the conference of the league.
The other implication with D'Antoni, and Lue, is that they are candidates because the players would approve of them. Joel played for D'Antonio, Lue has the LeBron seal of approval with Simmons. In the NBA star players run things, but our stars haven't ever earned that right.
The problem is there aren't any Pat Rileys or Phil Jacksons or Gregg Popovichs out there. You have to find the next Spoelstra or Nurse or Steve Kerr. And you can't discount Lue, supposedly he can be tough, and he has worked for both Phil Jackson and Danny Ainge.