no one working a 9-5 job ever became rich

I take this back. There are people that did become rich having 9-5 jobs, they had side hustles or generational wealth to lean on.

you can't really secure a lot of properties for the future generations if that's a concern.

If one lives with pessimism and no regard for the future generations, they can squander their money and not build anything at all. But if they want to pass something to the next generation of their family, they need to understand that it's a sacrifice to let go of today's worldly pleasures. I know there are exceptions like people scaling down their luxuries in life but some already have nothing trim down and they are already doing their best.

I think a mix of the two is deal, a 9-5 job with income invested in business/rental properties.

Yes, this is the way but I would put stress further on acquiring more assets whenever possible.