Are you asserting that children's math abilities have fallen? I don't think we are far enough past COVID to know the current trend, but math scores were not in general decline prior to 2020.
In my view, modern mathematics curricula are an improvement over rote-learning Euclid, and calculators are a useful tool.
Kids are allowed calculators only in quite limited amounts and special situations. At least where I see in real life.
I haven't been to elementary school recently, but I'm pretty sure kids are still taught to perform arithmetic in their head / manually before they're taught how to use calculators.
You should see what passes for what knowledge and skills a kid needs to graduate these days. It's sad.