Simmons is more talented than anyone in this draft, whether he's realizes that talent is another question, but athletic 6'10 forwards with his skills don't come along very often.
One and done guards rarely just step into a staring role, even a Fultz would probably be best suited to coming off the bench while he adjusts to the NBA 3 point distance and learning how to play defense (see Wiggins). So this draft will not make or break the 2017-18 season, Embiid and Simmons will decide how far they go next year.
And either they get the Laker pick this year or probably a top ten pick next year to go with their pick, and the Sac pick in 2019, so this year's pick won't make or break the team's future, either.
If Embiid isn't healthy, they'll have to build a championship team by committee, that is, Simmons and a bunch of talented but limited players (see GS).
Because Embiid is the kind of talent you see once a decade, Sixers will probably never get another shot even if they land a #1 (Towns is nice, but not the same level of talent, Wiggins, Bennett, etc.).
But if you have Saric, Simmons, RoCo in a front court rotation, you can still win with a Holmes/big boy combo if you add a couple athletic 3 & D guards.