My grandmother could multiply two three-digit numbers in her head faster than I can find my phone. She was not unusual. Her generation of bookkeepers, and they were almost all women, had to be fast at arithmetic, because nothing else could be. The calculator changed that. So did the spreadsheet. So, in turn, did every tool that came after.
There is a quiet trade involved every time we automate a cognitive task. We get speed. We give up an instinct. The instinct does not vanish all at once; it atrophies in stages, and by the time we notice, the muscle is gone. This is not a new observation. Plato makes it about writing in the Phaedrus, where Socrates worries that putting things in books will make memories worse. He was right, of course. He was also fine with the trade.
The interesting question is not whether we should make these trades, but how to make them with our eyes open. Which faculties do we want to keep using under our own steam, even when a machine could do them faster? For me, arithmetic is fine to delegate. Writing the first draft is not. Knowing the difference is a skill I am still learning.