AI is an unattainable goal, not because we'll never create it, but because "what is AI" changes over time as we figure out how to do things, and give them their own name. Decision trees, machine learning, deep learning - each of these was "AI" at some point, but now that we can do them the magic is gone and "AI" has become more distant than it was before.

(Heavily paraphrased from a longer post I read years and years ago, no idea where)