You know whats funny? Technically speaking, the only thing that holds luna from being a planet is only the fact that earth and moon are not declared as a biplanetary system. This is due to the weak argument that the mass center of the two planets is JUST under earths surface. When we argue with anything else, like for example gravitational pull, the sun pulls stronger than earth, making the moon not part of earths system but equally a part of the suns system, declaring earth and moon as a biplanetary system. Moon is very large in relation to earth to be an actual moon (like Jupiters or Mars’ moons). Strictly speaking by ignoring the (somehow) most relevant but weakest argument of the mass center being (just) inside earths crust, it could clearly be declared as biplanetary system