I don't think anyone expects them to stop developing. It's just that they are still developing. No, they are not championship caliber stars yet. No, the Sixers are not a championship team. Yes, the Process has failed, at least for now.
It's been one misery after another, truth to be told - draft miscues, trade miscues, firing Hinkie, hiring Colangelo, Colangelo's nonsense, Fultz, having no GM. Compared to all that Brand's attempts to remake the team just seem like normal basketball stuff, and yet it's still a good team (that probably would have made the finals last year with a little better luck).
Even at the time Simmons was drafted it was known that Embiid and Simmons (to say nothing of Okafor) weren't going to be an easy fit. But it wasn't even clear if Embiid would ever have a career back then, and you take the BPA.
Are these two guys not The Guys (at least not together) or have they been failed by the coach and GM? We're still gonna find out.