Solow Paradox
The main difference is that PCs actually worked as advertised, back in the day and the reason for this productivity dent wasn't a false promise from the start. Before AI the main use of computers was of a deterministic nature, meaning you get a directly reproducible outcome depending on the input. AIs (especially: LLMs) are probabilistic in nature, the output cannot be guaranteed to be correct, and it turns out just bolting on guardrails on top of the system is a band-aid. In practice, instead of getting a general-purpose intelligent machine which is capable of making autonomous decisions, you get a word predictor with an unlimited amount of possible failure modes.