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.