As an engineer, I believe I would know about some physics and science behind the rockets along with the entire project. Musk himself is mostly just a figurehead but what's important is he knows how to invest and is doing a phenomenal job at propelling the entirety of aerospace technology forward. If you think he solves most the problems on rockets and whatnot, you're sorely mistaken. Those jobs are for the actual engineers who develop the rockets and they're the ones who problem solve every little problem that comes forward during research and development.
Do you believe Musk is always working on the rockets? No, he gathers information from chief engineers assigned to any project and they tell him what they're working on, he then projects these summaries in interviews. That's how any business runs. There's the investor or founder, the chief engineers and technicians, engineers for different subcategories, and then down the tree we go. Everyone lower has to explain to their superiors and those superiors have to explain to their bosses, etc.
Back to your self landing rocket argument, if it is a publicity stunt or not, isn't it still a breakthrough? Isn't it still a step into the future where we are now capable of self landing rockets? If you're worried about fuel, we're also working on that but as everything else in the world boils down to, the problem is energy. If you break down any problem in the world, it comes down to energy and Musk had already proposed a solution to that issue in the form of a massive solar array. If you'd like me to go more in-depth on how everything is related to energy, you may ask.
Being a nuclear physicist gives you insight to physics and maybe general engineering but you also have to remember, they specialize in nuclear physics. Not engineering. Even if Musk himself gets some concepts wrong, but is he the company? Or are his workers the company? That's something that's misunderstood by a lot of people, he's not the chief engineer, he doesn't even have an engineering degree, he most likely just attends the meetings. However, all this should not downplay the fact he's one of the few investors to fund space research and development, which in itself is a very important step towards advancing humanity.
If you'd like a comparison, see it like this. Making fun and calling a person out because they're showing off their toy is not the same as making fun of and calling out the person who designed the toy.