Even the founders of the field badly misjudged how hard intelligence is.
"Father of AI"
Within our lifetime machines may surpass us in general intelligence.— 1961
Within a generation… few compartments of intellect will remain outside the machine's realm; the problem of creating "artificial intelligence" will be substantially solved.— 1967

The deadline came and went: progress was real, but nowhere near "substantially solved".
See also: Hyping AI isn't new