"ID isn't even a testable hypothesis."
Neither is evolution.
For example, many years ago it was much discussed that finding a "living fossil" would be a way to falsify evolution.
Then the coelacanth was found and they said it was a further proof of evolution, not a proof against evolution.
Please explain this strange concept. I have absolute no idea why this could possible contradict the concept of life forms changing over time.
New fish have developed over time, and the Coelacanth has survived extinction (barely) in it's ecological adaptation.
The fact that the Coelacanth is extremely rare, is a good example of why new fish have become better adapted for today's environment. What was so surprising, is that it had survived so long!
I've never heard of a "living fossil" possibly falsifying evolution. Indeed, evolution doesn't say anything about the duration of species, but only that populations change over time in response to environmental pressures. Methinks you either misremembered the statement, or that the statement came from a creationist website -- the latter are notorious for making stuff up from whole cloth.
Finally note, the two modern species of coelacanth are not identical to the species found in the fossil record, but are very closely related.