I think it's tough to coach a team without a clear hierarchy. Deep, talented teams without distinct roles may struggle a bit, especially with free agency on the minds of various players.
But, as a counter-point to your thread title, think Luke Walton and the Warriors.
Seems like a bad example - Warriors were on auto-pilot from a coach who had already organized the talent and the players knew their place in the hierarchy. I think OP makes a very good point - this team is a bad mixture coming back together in an awkward way at disjointed places in their careers and a coach who really has not ever coached superior talent in college or pro. We may look back on this eventually and see that these struggles were inevitable.
I just disagree. If it's much harder to coach talent, then the Warriors are the poster child, right? You have Curry, Thompson, Green and Durant all in their primes, plus extremely talented depth guys like Iguodala, Livingston, etc. Yet, a rookie head coach led them -- without Durant -- to a 67 win season and a championship. Then, Walton -- a rookie head coach temporarily elevated -- led them to a 39-4 start the following season. Then they added Durant, and won another title, followed by another.
Me or you could coach the team, and they'd win 60 games and a title. Because, it's not much harder to win with a talented team.
The problem isn't talent. It might be selfishness, it might be role confusion, but it isn't because of having too much talent.