and people got worse at mental calculus when calculators when invented.

That may be true, but that is a much more limited problem, than losing some of our ability for critical thinking and problem solving in general.

ai, meanwhile, or at least the ai we’re sold, does not offer significant advantages

This is very true, the AI are shown to even hallucinate, and give incorrect and harmful solutions. A calculator does NOT do that.
So not only is the AI a danger to our critical thinking, we actually need it MORE when using AI.