Hard to find longevity or stability in a role that exists to fail
The only way you can really get better security at a company is to have an ingrained security culture. I.e. developers are continually educated on secure coding practices and new threats, code reviews include security checklists, corporate security training includes continual social engineering tests and an atmosphere of continual improvement.
And yes, that stuff does cost money, but that's rarely the resources I see CISO's fight for. Instead, they fight for lots of expensive software, things like useless, shitty WAFs or poorly built "network monitoring" software (which can be a huge threat vector in itself, just see the SolarWinds fiasco).
Like many other comments here, I don't believe security is something you can "bolt on" at a company. Yes, there are specialized roles that a dedicated security team needs to fill, but unless everyone at the company has a true understanding of the value and importance of security vigilance, you're screwed.
It's probably like the old saw about advertising. Half of all it is useless, we just don't know which half!
I strongly agree though that you can't really bolt on security, it needs to be designed in and part of the culture as much as possible. You'll never get everyone to understand the value though (I wish!).
Can I have a checklist please?
Full stack web dev
Edit: Here I found one https://www.michaelagreiler.com/security-code-review-checkli...
But as list of things to consider, if you already understand what you're doing, its not too bad.
So either the company does well and the CMO stays, or not. And the default for most companies is to fail.