If the shape of the menorah has evolved, that is only evidence that the shapes of symbols (as well as the shapes of objects constructed for specific purposes, which menorahs also are) evolve. Which we already know.
The evidence you need to support a claim that "destroyed Atlantis = menorah" is something else in Jewish culture that makes the same connection. For instance, does the festival associated with the menorah commemorate a past land lost to inundation (such as, the earth before Noah's flood?) No, not by any stretch of the imagination.
Is there anything else in Jewish culture that suggests Atlantis? Perhaps the Noah story itself, which is after all a story of escaping by ship from a land punitively inundated by a god. In fact, that's far better evidence than the menorah shape. But it's still not very good, because there are a lot of differences in the story as well.
But wait, there's more! There's also the story of the infant Moses, left in the rushes at the verge of the Nile in a basket to escape a pogrom. There's no island involved, and there's no ocean, and no sinking or inundation, and it's not clear whether the basket ever even floated on the river at all, but so what? It's all symbolic! Baby Moses represents the scattered seed of lost Atlantean civilization, arriving in a symbolic ship (a basket) upon the shores of Egypt (symbolized as the banks of the Nile) and being adopted into Egyptian culture. Stories evolve too, so you can't prove it wasn't originally about that, long before it was written down.
Damn, "making connections" sure seems easy. But maybe I'm just really good at it. Do you think Cameron might give me a few hundred grand to go tour Mount Ararat and the banks of the Nile with a camera crew, to see what else I can find?