Marking this thread for a more thorough response later.
I went to Morocco in January 2024 for just over a week. Not long, and I didn't really have any predispositions about exactly what I wanted to see. I ended up spending some time in Marrakech and then doing a 3 day tour that took me from Marrakech, through the Atlas Mountains, out to the edge of the Sahara, then up and through to finish at Fes (didn't get to see Fes, as had to leave early the day after tour drop off).
If I had more time to spend, I'd be very happy to see Fes, Tangier and more of Casablanca. In a sense, sometimes it might feel like "more of the same", but at the time they were genuinely fascinating, and while Morocco's train travel isn't much to marvel at at all, it generally was easy going to get between major Moroccan centres.