Steve Keen and many others keep trying to scare us with charts like the one below showing the rise in private debts over the last twenty years or so.
One reason for not being scared is that interest rates have dropped significantly over that period. Thus, (surprise, surprise) people and firms borrow more.
As to what would happen if interest rates rose again, well, if they rose at the same gentle pace that they've declined over the last twenty years, that wouldn't be a problem. In contrast, given a SUDDEN rise in interest rates, obviously, there'd be problems: some mortgagors would go bust, as would some banks which had loaned too much to high risk borrowers.
That would cut aggregate demand, but that's easy enough countered with standard stimulatory measures. Of course, many governments and members of the economics profession are too dumb to realise we have the power to counter recessions. But at least in theory, recessions are easily countered.
As to banks going under, well, small banks in the US are covered by the FDIC.
As to larger banks in the US, and non-insured banks elsewhere, the fact of banks going under being a cause of macroeconomic problems just proves the idiocy of our existing bank system. The solution is full reserve banking. Under that system, it's plain impossible for banks to go insolvent, though it's perfectly possible for them to see a sharp fall in their share prices, resulting perhaps in being taken over.
And finally, I'm still waiting to hear some FUNDAMENTAL THEORETICAL reason for thinking debts are too high. But never mind: I can come to the rescue there. I set out a basic and very simple reason for thinking debts are too high here. The reason is that the debt creation process is subsidised by taxpayers!!
How's that for simplicity? To be more exact, I argue at the above link that money creation (aka money printing) by private banks is subsidised, and given that for every dollar of that form of money there is a dollar of debt, it follows that in subsidising private money printing, we're subsidising debt creation.
So… if we abolish private money printing (which is what full reserve banking involves), the result is something nearer the optimum amount of debt, plus we're more likely to avoid bank problems giving rise to macroeconomic problems.
What more do you want?