They need to run more. I really think they should try to be like the Showtime Lakers. Obviously Simmons and Embiid aren't as good as Magic and Kareem, but they need to run the floor and use their size advantages on the break and then if it fails, use that size advantage in the half court.
Can they though? Embiid wears down late in game and may not be able to take the pace with his trick knees. But it would definitely help Simmons, I agree.
Agreed, Embiid can't really run like Worthy/Cooper/McAdoo/Rambis/Green/Scott. What Embiid can learn from the showtime Lakers though is to develop a scoring move that's impervious to any kind of defense like Kareem's skyhook. Kareem is in elite company among All-Time big men on offense-he was probably the only one aside from Shaq who could be an elite offensive centerpiece in both the regular season and playoffs while meshing well with star talent who need the ball around them. Here's a graph showing how the very best big man legends stacked up against each other on offense, and Kareem/Shaq stand out from the rest with their combination of volume and efficiency to go along with strong creation:

Although Duncan and Hakeem are also very impressive, they are hamstrung by their isolationist tendencies and subpar to mediocre vision compared to their contemporaries (Dirk suffers from a similar problem as well). Their creation numbers are inflated due to teams running the entire offense through them and surrounding them with shooters for easy kickouts when they're doubled to make life for them easier when it comes to creating shots for their teammates, while Shaq and Kareem got the bulk of their creation numbers through utilising their passing and vision to exploit gaps in the defense. If Embiid can develop a scoring move like Kareem's skyhook and clean up his passing/vision (his passing is also problematic at times), he could be one of the very best offensive big men in NBA history.