Why is the classification planetary nebula considered a historical misnomer in astronomy?

It describes the glowing remnants of a dying star rather than an object related to planets.

The term planetary nebula is an artifact of early astronomical observations. When early astronomers viewed these glowing, circular structures through primitive telescopes, they resembled the appearance of planets like Uranus or Neptune. However, modern understanding confirms that these structures have nothing to do with planets. They are actually the outer layers of a star being shed during the final, terminal stages of its life cycle. As a star like our Sun exhausts its nuclear fuel, it expands and ejects its outer atmospheric layers into space, leaving behind a glowing, expanding shell that serves as the visual remnant of a dying star.