To quote JJ Reddick quoting Doc on Twitter, I think there is an issue of cooperativeness with the last few Doc Rivers' team constructs. If Doc is saying the Clippers "didn't get along well enough as a group", I felt the lack of harmony in this Sixers team throughout the season as well.
You are correct though that this is definitely a deep enough team to run it back for the most part. If I was the Sixers organization, I'd seriously consider a different PR team or some such ways to create a better culture within the organization and its fans. (Personally, I'd also consider replacing Doc but that's my NBA 2K Franchise mode player in me talking...)