Obviously Simmons and Embiid are both really good.
They still need to fill in the roster though. They currently have a bunch of place-holder shooters (Reddick, Bellinelli, Bayless, and Illyasova).
ROCO can probably fit into their long-term plans, but he is basically James Posey. I'm not sure he can be the 3rd-4th best player on a championship team.
I like Saric a lot, but playing him next to ROCO, Simmons, and Embiid forces one of them to defend down a position or two, and it isn't easy to chase little guys around screens all game.
Fultz may be the third guy, but with as NBA-ready as Simmons and Embiid are, how long can they wait on him to be ready to compete on both ends in the playoffs.
The Sixers definitely have a good team, but they also have quite a bit of roster formation to go in order to be a true contender. They have the assets to get there, but we'll see if they do.