The Lakers expect to be in the hunt to sign Paul George and/or Westbrook, and they have a young core of Russell, Ingram, Randle, Zubac, and likely Ball. They have plenty of possibilities for major improvement.
As for the Sixers, I agree, it all hangs on Embiid's health. He's the top cornerstone on any of these 3 teams if healthy, but the health is a big if. He's a transcendent player who can easily make them a contender if guys like Simmons, Saric, and whichever PG they pick up in this draft maintain good chemistry with each other. Also, they have a TON of cap space.