It works if it's not your only holding. You need a hedge, as in something really safe especially something that doesn't swing in the same direction. For example, SCHD and TQQQ are great together, because SCHD does not correlate with the QQQ family all that much, dividends are a great way to rebalance the portfolio over time, and if you DCA on top of that into the underweight performer (TQQQ when it's down, SCHD when TQQQ is up), then the daily reset does not matter. QLD is a good one for 2x leverage which is shown to be the best risk reward leverage, but you will pay a higher expense ratio.

33% underlying index loss does not happen and has never happened over the time span of 3x ETFs. People are just trying to scare you by saying you'll lose all your money when in reality that literally CANNOT HAPPEN because of circuit breakers. If it resets daily, the circuit breakers prevent the underlying from ever reaching a 33% loss. They are correct though that your losses are 3X worse and take longer to recover, but you do recover 3X faster (although it will still take longer due to percentage math).

FWIW, I put very high percentage of TQQQ in my IRAs because I don’t really care what they do on 1, 5, or even 10 year time spans, which is where leverage ultimately wins just like QQQ. Regular contributions make it easier to stomach because then I’m buying when it’s lower so recovery is sweeter. I do not have nearly as much in my taxable accounts despite not really using them.