It’s a sophisticated technique that requires a great deal of care. Leverage works both ways. It can wipe you out quickly. So, for someone who is carefully investing using it, and fully engaged, perhaps.
A good friend, a retired Marine, trades futures and options. Every day. Every day he gets up at 05:00, reads the WSJ, watches all the financial news channels, and puts his orders in before the market open, then goes fishing (the fishing part is on most days, not all).
He does well. He no longer needs to work.
But when you look at the hours he puts into the effort, it is nearly a full time job.
For him, sure, trade on margin, he is a full time investor.
But for the other 99% of us? We don't have the time in our already busy lives to pay close enough attention.