The Sixers have a lot of talent (Fultz included), but as a team they have to take much better care of the basketball before they make any noise. 19 TOs tonight, and they average more than 17 per game on the year. That's too many possessions lost and too many chances at easy points for the opponent.
Simmons and Embiid both average 4 per game individually. That's tough. As a team they aren't efficient enough offensively or good enough defensively to absorb a disadvantage like that.