My emphasis on collateral was to explain the circumstances that led to the housing bust.
Putting 100% of the blame on the lender just seems silly and, quite frankly, like you know jack shit about lending.
First, loan documents are actually not that complex or beyond a typical consumer's comprehension. That's condescending IMO. A borrower should be able to look at the LE, CD, note, and DOT and know how much they're borrowing and what the monthly payment will be, as those things are clearly spelt out. So are interest rate and fees. The rest of that mountain of legal docs is mostly standard for every borrower. And while lenders can and should say no to a borrower whose DTI is excessive, it's still up to the borrower to decide if they're comfortable with that payment. Just because they can be approved for a particular payment doesn't mean they should accept it.
Second, lenders don't and can't control the borrower's choices. Lenders don't pick the collateral, for example, they only obtain title and appraisal to determine that it's acceptable collateral. But those things won't tell us if, for example, the HVAC is going to go out 10 months later, hitting the borrower with a huge bill that will affect their ability to repay. And no amount of documentation and analysis is going to mitigate the potential risk that a borrower might get laid off, or divorced, or transferred or whatever.
And finally, people are responsible for their own actions. So of course, lenders should not make loans that they know have low probabilities of repayment. Or engage in lending practices that might lead to market bubbles. But at the same time, there is no such thing as a loan with a 100% certain probability of repayment, if only because inevitability the choice to repay belongs with the individual borrower.
Lending, at the individual loan level, is not a science. It just isn't. It can't be.