To be fair the 13/14/15 drafts were not all that good, but I think they took the best route by taking BPA.
The 2013 draft had the Greek Freak (Best player in the class by far) and Gobert (drafted late first). Otherwise the whole draft has a bunch of role players and busts. Can't really fault the Sixers for their picks.
The 2014 draft they got the best player (Embiid). Had it not been for his foot injury he would have went #1 overall.
The 2015 draft had a lot of talent and they got the number 3 pick. Towns is probably going to be the best player and he went #1. If they landed the first pick a Towns/Embiid can work. Otherwise you have Prozingis (really good player and maybe will challenge Towns as the best player in the draft class but I would rather have Embiid). I don't think Embiid and Prozingis can play together. In hindsight they should have drafted Booker who is really good and will only get better. Okafor was the correct pick at the time but he just has not developed. Is another brook Lopez who can score in the paint but does not contribute much else.
If they land a top 5 pick this year (through the Kings) they will have a contender going forward (assuming everyone stays healthy which is a big if). Embiid/Simmons/Top 5 pick is a great core. Covington is a very good 3&D player that any championship type team needs to have. They have other first round picks as well to add depth to their roster.