Easier been said than done.
People already know this and some are already working on it. However, it's not that simple and people can just start right away as we are living in different life standards. And even some already owned an investment, working will not stop there. They still have to manage it along the way.
Investment is not a joke and to start it just to hope for a literal passive income isn't a good idea for me. People should invest to have a stable and regular source of income and not to rely on passive ones. Of course, it needs works but it's happy to work on something that we owned that generates a regular and good revenue. The effort and time spent is worth it.
You are right, easier said than done. Also, passive income most of the time ended up not really passive as along the way, it stops for no reason. I don't believe in passive income as there are so many factors that will contribute to sustain its lifespan. And if one factor is not working, the chain would be derailed and goodbye to passive income that you are waiting for. And in terms of investment, not all people are lucky with this area. It takes a lot of experience and skill to get positive results from this.