Calculators don't do math, they do calculating. Which is to say, they don't think for you. There's not much value in being able to quickly compute some expression in a world with calculators. But there's a huge value in knowing how to know which numbers to feed into the calculation.

The biggest problem with calculators (rather than slide rules), was that because calculations with big numbers (large mantissa) were so easy, people got used to doing them that way without consideration.

Using a slide rule meant inherently knowing order-of-magnitude, rounding, and precision. Once calculators make it easy they enable both new kinds of solutions and new kinds of errors (that you have to separately teach to avoid).

At the same time, I basically agree. Humans are very bad calculators and we've needed tools (abacus) for millennia.

I derive tremendous value from being able to calculate taxes, tips, and so forth in my head, or right on the receipt, without having to reach for my phone and launch Droid48. (I know some of y'all are also Droid48 bros.) It's even more profound a convenience than knowing how to drive Emacs with just the keyboard and not having to reach for the goddamn mouse.