Things can get really bad really fast. 2001 bust, followed by housing crisis, followed by the oil crisis, then there was brexit. enough number of people feared enough and big money finds a better place to park their $, the downward spiral feeds itself and make things worse than they actually are.
Wall street will always unlimited supply of triggers to evoke the fear among people and sometimes they just have enough mass line up behind them and boom you have economic crisis out of nowhere.
If next housing bust were to occur, it may not be due to subprime lending. It may be due to, say, people lost jobs, not getting raises and choosing to let go of their expensive houses than rob their retirement. If anything, the previous crisis set the tone among people that it is okay to walk away, there is no shame, it is not even end of life, banks and feds will bend over, and one can always buy home in a period as short as 2-3 years again!