No, he doesn't have a point, it's the same thing we've been hearing since 2008. There's no 'essence' in Mewtwo's replacement because Lucario is not an intended or spiritual successor, no more then PT or any other Pokémon that made it in ahead of him. Also, there is damn good reason he wasn't replaced, we have data showing he was the farthest along of any other cut character, that is not inarguable. Why would Lucario replace a character he was more then likely made alongside with?
Yes Lucario is playable and Mewtwo is not, but guess what? So is PT (special note since he's also a newcomer), and Jigglypuff, and Pikachu, they're playable because they made it in, Mewtwo was just unlucky, that's it. Really, Lucario is just a scapegoat, people saw some surface similarities and latched onto them when in reality, he's no more guilty of "replacing" Mewtwo then any other character.
It baffles me this is still being pushed. This has been refuted so many times I've lost count, honestly there's no good reason to believe Lucario replaced Mewtwo in whatever meaning of the word, at least not anymore then PT or any other character.