So, you've kicked the can for 10 years; now it's time to pay back. Where do we get the money now? If you cancel it, you're destroying the retirements of millions of Americans, not just hurting some abstract entity of "the Market". Remember that a large number of people feel the effects of a market downturn, even if through a retirement account or pension plan.
So, to avoid retirees eating dog food, you now have to pay back. How do you propose to do this, given we already have a truly colossal $23.6 trillion in debt?
[0]: https://www.thebalance.com/who-owns-the-u-s-national-debt-33...
now you are asking how do you pay it back? well you could start by taxing some of the ~600 billionaires that live there. the top eight richest billionaires own as much combined wealth as "half the human race".
so it's not like there isn't a pot of money there, and taking some of it certainly is not going to cause those people hardship. now you look at some of the major corporations and they're very low tax compared to revenue and profit and you have another pot of money that you can access again without causing too much hardship on the company.
the money is out there it's just very unfairly distributed.
if you were at war with a foreign country, and they were killing and injuring your population, you would fight back, the economy should be shattered, but you fight the war and when you win you rebuild. that's what this is, a war. it's just the enemy is not quite the same as it has been in the past.