The issue is that we tax labor. Creating a company is a choice. People who survive off trading their labor have no choice. They have to perform labor. Taxing survival is inherently flawed.
You only need a profitable side hustle because you're being underpaid and stuck in the capitalists' system. This side hustle is already taxed like a company, it would be on you to structure it so you are a laborer of the company while also covering the company tax.
Investments aren't labor so they can be tax as they are now.
The main problem is that you can't imagine a system that doesn't have a personal income tax. I don't have the time or patience to go through their history of this so I'll leave that as homework.