In the short term it will always look stupid. Borrowing allows you to invest, which leads to growth, which allows you to borrow more.
But debt also accumulates, and usually faster than GDP growth. Until debt servicing starts eating your budget. Which is a slowly encroaching killer
I find it difficult to draw conclusions just yet. Yes, Germany is under-investing and that hurts. But with another 20 years of hindsight it might look like the lesser evil
https://youtu.be/ajH6YVhdOZU?is=Xht8Qsd_eGqnS7wW