Its not Atlantis because there is no/was no Atlantis!
There is no evidence, no not any, evidence for the existence of any advanced civilization other than those that we know of (in general terms) from up to about 8 or 9 thousand years ago.
If there was such a civilization it left not a single trace and had no influence on any subsequent civilization and fits not into any pattern that would make any sense of it.
Ptolemy's description was written only 2 thousand or so years ago and is utterly fanciful. He was further removed by at least 4 times from what he described than we are from him. Whilst in general terms some of his writings are a useful guide to history near his time, at best, even with contemporary events he is notoriously unreliable. Why then should any credence be given to his report.
So what else is there. Pretty well nothing. If the stories are true the Atlantis story is way out of whack - even on the level of continental shift. There are no disappearing landmasses, certainly not of continental size, during history or human prehistory, save perhaps the Bering Straight. (If i remember rightly that was a crossing about 10 and 20 thousand years ago, but I may have that out a bit).
There are submerged cities and all those discovered can be associated with adjacent civilizations. Would it not be odd that an advanced technological civilization left no physical or other trace whatsoever?
Some will say that none of this is proof that Atlantis did not exist. That is sorta true. But I would say where is the proof, any proof, that it did exist?