For example: I don’t believe in the axiom of choice nor in the continuum hypothesis.
Not stuff like “math is useless” or “people hate math because it’s not well taught”, those are opinions about math.
I’ll start: exponentiation should be left-associative, which means a^b should mean b×b×…×b } a times.
1 should be a prime number.
It was once, but got kicked out due to new discoveries and equations I’m not smart/mathematically trained enough to understand.