The simple way to think of it is that there is a bill to pay, and it will be paid. We put it on the government account because no other entity in society can borrow as much money at such low rates. Then it gets paid over a span of many years, maybe a decade or more. But paying it means either higher taxes, lower spending (services) or inflation, or a combination of the 3. Higher taxes as the main source is probably the "best" way to do it, but people need to review the make-up of the GDP again to realize that just "tax the rich" isn't even enough to cover something of this size. Everyone who has an income or buys products will be paying added taxes to what they did before. The worst case scenario is that the near-term disorganization of your economy due to job losses and business foreclosures means that for years you're stuck at lower output/GDP and high unemployment.That is true. Going 18-24 months with handicapped economy is not something you can climb out of by government stimulating economy. Even 2-3 months is a massive gap to catch up, as it virtually means most households will lose their income for that period and will have it significantly reduced in the months following lockdown. Obviously there are a lot of people who can survive that but there are many times more who can barely do that. And conspiracy nutters actually believe someone will benefit from it.
Another thought experiment to think through this: if you were living in a fully socialist society where the government owns all enterprise and you don't have personal or corporate debt, but you still have a currency and wage rates for how much people are paid, right now you would be asking people in the essential parts of the economy to continue working while those in those that can't operate sat at home to the extent that they couldn't be redirected to other functions due to lack of expertise or sheer logistics. But you would actually have to pay the people still working (and probably working harder) less than you did before, because you need to account for all the other goods and services that aren't being produced so they can't consume. Even in that situation you realize there is always a cost to be paid for shutting down a large part of the economy for any period of time.