Which muscles are massage guns actually good for?

I am trying to understand what a massage gun is actually meant to be used on before I buy one. Most videos make it look simple, but then every safety warning says to avoid bones, joints, the front of the neck, and anywhere too close to the spine. Are these mainly useful for bigger muscle groups like quads, calves, glutes, hamstrings, and maybe upper back/traps? Or do people also use them safely for desk-related shoulder tightness?

I sit all day and lift a few times a week, so I am not trying to do anything aggressive. I just want to know which areas people actually target in real life, and which areas are better handled with stretching, a ball, or seeing a professional.