You have to prove that the defendant did it. You can't use a process of elimination. Saying "these three people didn't do it" is not even close to saying "the fourth one did".
The problem is that you're taking all the evidence in a vacuum piece by piece, rather than looking it as an overall whole (and i'll say that florida did a poor job at presenting it as such)
Is the 31 days of partying enough to convict? Maybe not, though I think, as you said, if you replace "Casey Anthony" with "Bubba McHardhat" then Bubba is on death row atm. That is essentially the same kind of evidence that has Scott Peterson on death row.
Is the constant lying enough to convict? No.
Is the chroroform and other searches (or even the searches in conjunction with the amounts of it in the car)? No, though a tentative yes if there was more of it (also the idea that Cindy made those searches was pretty conclusively exploded, and Cindy couldn't give a straight answer as to why her work PC was logged in while they were being made)
Is the duct tape and the other missing items from the Anthony home enough to convict? No.
Is the smell of decomposition and Caylee's hair enough to convict? No, because it is true that Caylee could have deposited that hair while she was alive, and hair-banding is really new forensic science that can be questioned by a determined defense. However, NORMALLY cadaver dogs have a near 100% hit rate.
But all of this evidence taken as a whole implicates Casey, probably beyond reasonable doubt. Reasonable doubt does not mean "every shred of evidence is air-tight and irrefutable", it means "based on the evidence, why would we not conclude the prosecution's argument was true?" There is simply no reasonable examination of the evidence that can produce an explanation of Caylee's death other than "Casey Anthony murdered her". The best the evidence can produce is "it's theoretically possible something else happened because all the evidence for the prosecution was not rock solid, but there's little/no evidence suggesting that something else happened other than pure speculation". And that's what the defense was - various speculation as to why a given piece of evidence might not be that strong or might not offer conclusive proof, while ignoring the various "coincidences" that all centered around Casey Anthony.
btw, you don't need cause of death to prove murder by any means, you don't need fingerprint or DNA evidence to prove murder, you don't need eye-witness evidence to prove murder (and eye-witness evidence is honestly unreliable compared to most circumstancial evidence).