Less than 10 yrs age gap should be fine, in my humble opinion.
Discussion
I’m at an age where 10 years younger than me is very different than 10 years older. I also know men my age that routinely date 10 years younger.
Women should never date younger, if you do it needs to be only a few years (like 2 max).
We mature much faster than men.
Men can date significantly younger, though 40 & 17 is just wrong.