Fractional reserve is also regulated and deposits are insured up to a certain amount, so it's definitely not comparable to printing imaginary USDT - even if fractional reserve banking has many well-known issues.
Fractional reserve banking is not what failed in the financial crisis. Multiple things failed, including credit ratings, mutual funds/pensions/etc investing in high risk investments, etc. The biggest risk people think of for fractional reserve - they won't have the money when you need it, a run on banks, etc - didn't really happen in the states in any significant fashion.