If by classical investments you mean vanilla stocks and bonds, those are heavily regulated with strict disclosure and transparency requirements, heavy penalties for cheating (insider trading), and standardized reporting for de-obfuscation as much as possible.
If you're referring to more exotic instruments, those are off limits to mainstream folks, only available (in the US at least) to accredited investors with enough discretionary wealth they won't go homeless if they lose their investment.
In either case, a lot of effort goes into mitigating the cognitive load for mainstream non-expert investors.
What about those things that produced the last financial crisis? Reselling bad credits b mixing it with good credit and so on. Maybe it was only accessible to the pros, but then if they got it wrong, and they probably bundled it up with other things that they were then able to sell to the public.
If you're referring to more exotic instruments, those are off limits to mainstream folks, only available (in the US at least) to accredited investors with enough discretionary wealth they won't go homeless if they lose their investment.
In either case, a lot of effort goes into mitigating the cognitive load for mainstream non-expert investors.