It's not that Wall Street gives you warning signs. They literally tell you "this is a probably a bad bet, and you should not take it" in the descriptions of most products. Very few people actually read those descriptions, despite the fact that they really should if they are buying weird financial products. The banks tell you to read them. And yes, a mortgage is a weird financial product.
For example, people who lost a lot of money holding XIV (a leveraged inverse-VIX ETN) had the warning about not holding the thing overnight in bold red text in the prospectus. People holding leveraged CDOs and every kind of CDS had all kinds of warnings in big bold text in their prospectus. The good old "liar's loans" of the early 2000's had big bold text saying "it will be bad for you if you lie about your income."
Pretty much the only financial products that don't come with big bold text saying "you are an idiot for buying this" are single stocks and the most boring of ETFs/mutual funds (eg SPY).
Contrast that with the warning signs from crypto projects, which are a lot more oblique than big bold text in a document that they tell you to read. Wall Street screws you, but they generally do it slowly and they tell you how. Crypto projects just straight up steal your money one day out of the blue and run to Dubai.
CDO2s backed by worthless subprime loans were put into AAA rated bonds. I'd call that an outright scam. For that matter all versions were far more risk than they claimed they were, given that they were worthless, even if there was some fine print somewhere.
I don't have an ISDA with a bank or a copy of a CDO-squared prospectus, but it's hard to imagine that there wasn't a big warning about them being a leveraged product that you should not invest in long-term.
The rating agencies did not understand the products they were rating. However, the warnings were almost certainly on the label.
That's why the rating agencies were sued over this, and not the banks.
A rating inherently claims understanding though. Is a bridge safe to walk on? Some guy who doesn't understand engineering is putting signs on it rating its safety. Ignorance is not a defense at this point.
They did sue the banks. For many things including inflated appraisals of the loans.
I'm sure they have some kind of warning for everything that isn't FDIC insured. But misrepresenting high risk as low risk instead of zero risk is just a quantitative difference. There are plenty of scams that do this. for example just lying about a company's earnings. I suppose the precise crimes they charge them for may differ a bit.
