You are correct that GDP-to-Debt wasn't really used much prior to the Greek debt crisis because the pre-marxist/leninist brainwashed generation understood finances/economics a lot better than the current people in power.

It doesn't matter if your GDP-to-Debt is 0%. $1 spent on a value-loss project, is a waste of $1. That was understood 40 years ago. It is no longer understood by most people.

Most people don't understand how if you pay someone to produce nothing $1 from debt you cause inflation which reduces the buying power of everyone else in society (because you've increased demand by $1 without increasing supply) and you now have an interest payment of $1 which is a wealth transfer from the public (who gains no value) to debt-holders. Value-loss debt makes the public poorer, while only the debt-holders are able to mitigate the loss of wealth. The net impact over the long-term of value-loss debt is that society as a whole is poorer for it. This seems fairly simple but leftists do not understand it and their current MMT ideology is that we should be maximizing government debt to maximize employment but what they fail to realize is that as you take on debt to maximize employment you reduce the value proposition of this employment. Just because you're digging ditches and have maximum employment doesn't actually mean you're adding anymore value to society than more unemployment and less ditch diggers (in many regards you're actually lowering over quality of life for citizens because you're causing inflation for productive workers while unjustly redistributing this wealth to unproductive workers which is inherently unjust).

Most government debt these days is absolutely terrible. Very little government debt is actually value-add for society anymore. Propping up failed businesses that failed due to government regulations and then giving money to people who aren't working so they can buy new cars... it's an absolute ridiculous waste of money that is dragging the well-being of productive people down immensely. We're destroying the strength of our economy. We need to abolish public education, lower taxes, reduce military spending and stop taking on any new debt.