I decided to launch products several times (alone or with 1-2 friends) and, while I got some decent passive revenue, I was able to reach 250k per year profit only once - and not forever, that opportunity actually dried up completely.

My startup on which we poured 3 years of work by 10 people, failed to ever earn back the money spent on it.

I think you are underestimating how hard it is to sell and how fleeting can success be.