Living organisms that aren't based on something resembling DNA/RNA would be just as big a deal as extraterrestrial life, and I don't think the labeling of such

Living organisms that aren't based on something resembling DNA/RNA would be just as big a deal as extraterrestrial life, and I don't think the labeling of such organisms as 'alien' is misdirection. Now, if it proves that they're merely DNA/RNA based organisms that happen to metabolize arsenic, that would be a biological whimper, as yes, they're just an earlier branch in the evolutionary tree. However something that appears not to share a common ancestor with the rest of life on the planet would be a huge deal.