I would not invest long term using margin. The interest rates would likely eat any profits unless you got lucky on a bet.
Short term, though? Nah, you should absolutely trade on margin.
I started investing in 2020 immediately after markets hit rock bottom from COVID. Margin multiplied my gains as I bet on the market bouncing back.
You could certainly argue that I was just lucky. I could have easily been wrong and it's possible markets could have taken a longer time to recover than I expected. But tbh, the market recovered significantly FASTER than I expected.
By definition you're risking more than 100% of your portfolio value when trading on margin, even short-term. One wrong bet can wipe you out. You shouldn't delude yourself to believe that this isn't the case because you've had one successful experience with it.
Risking getting wiped out may be a palatable prospect if you're early in life and have the time to rebuild your fortune, but it won't be if you're risking 20 years of savings.
In the market timing is both 1. everything and 2. impossible to predict without cheating.