As far as the NBA is concerned, a lot of these fanbases and franchises are desperate to win, so they assume that signing or trading for older, experienced stars will somehow lead them closer to a championship because the keyword is experience.
In the Sixers' case, the fans thought PG, on paper, would be an immediate upgrade over Tobias Harris, and based on PG's resume of being a star and having seasons/postseasons of elite performances compared to Harris it seemed like a win.
In PG's defense, and to some extent Embiid, both of them came into the season injured, so I wouldn't say either one of them is washed. Paul George is still capable of averaging 18-20ppg, and Embiid can still have dominant performances; as we saw last week, he had a triple-double. This season just wasn't their year; it was a disaster since October; I expect them to be better next season.