Everyone is capable of, and can benefit from, mathematical thinking

I agree with the sentiment of this. I think our obsession with innate mathematical skill and genius is so detrimental to the growth mindset that you need to have in order to learn things.

I've been working a lot on my math skills lately (as an adult). A mindset I've had in the past is that "if it's hard, then that means you've hit your ceiling and you're wasting your time." But really, the opposite is true. If it's easy, then it means you already know this material, and you're wasting your time.

Most people don't try hard at the gym. Most people don't try hard at music. Most people aren't comedians.

This reads like the foreword to the incel handbook.

And that's obviously bad because incels are not real people with feelings.