Facial expressions are a good fit and there is really nothing much speaking against using morph targets here. The other use cases you mentioned might give you some grief, though. That’s because morph targets interpolate linearly, which means you won’t be able to create any circular or rotational movement with a single morph target.
Take a compartment door. If it’s supposed to open like a regular door, rotating on hinges, morph targets won’t give you that. On the other hand, a sliding door will work just fine. Same with jet engines. If you want them to move between forward, left, back, and right in a rotating fashion, you might have some trouble making that look good with morph targets. Jet engine parented to a single bone will probably yield better results.