The same will certainly apply to the intra-head security you want against fake content and propaganda.
The cyber security market was valued at USD 153.65 billion in 2022 and is projected to grow from USD 172.32 billion in 2023 to USD 424.97 billion in 2030, so apparently people are buying cybersecurity solutions.
The rest looks much more like services than products.
The fact that one of the fastest-growing markets is omitted by YC is shocking to me. The opportunity to build $1B companies, which seems to be one of YC's acceptance criteria, is enormous.
I don't know how far or close you are to the security field, but I do share your sentiment that many tools and so-called security solutions are useless and don't solve the problem. So it's now even more necessary to go and build new solutions. The problem persists and grows.
Anyway, I do agree there's plenty to work on the solutions. But those will probably come from areas like "correctness", "user empowerment", and etc. The closest I see to it is "policy enforcement".