>>31489109>>31489142No, as legandary / mythical is a terrible indication of power and viability. Meloetta was RU, Celebi was UU, Shaymin base was UU, probably going to be RU as it was BL2 in Gen 6, and Keldeo is currently in UU. Regigigas is a PU shitmon, and the other regis suck as well. Two of the legendary birds are PU. In terms of cover legendaries, they are all ubers anyway, with the exception of Kyurem B (no reliable physical ice STAB bar icium Z) and Kyurem base. Do you really think Guzzlord poses any sort of threat in competitive?
TL;DR A pokemon being legendary or mythical is an arbitrary label that has zero meaningful correlation with competitive viability.