I didn't say anything about the ideal savings rate being 0%
The quantity of savings is divorce of the quantity of money available for investing or, in other words, lending money doesn't come from savings. That's an empirical fact.
Of course, households and firms are going to choose to keep savings, and that's OK. If people choose to spend more and keep less savings then, Central Banks could accommodate the Interest Rate in order to make lending more expensive and avoid inflation, or the government could increase taxes or some other solution that retires money from the economy.
The quantity of savings is divorce of the quantity of money available for investing or, in other words, lending money doesn't come from savings. That's an empirical fact.
Of course, households and firms are going to choose to keep savings, and that's OK. If people choose to spend more and keep less savings then, Central Banks could accommodate the Interest Rate in order to make lending more expensive and avoid inflation, or the government could increase taxes or some other solution that retires money from the economy.