In this scenario, Elon Musk would never have shot the world's most advanced rocket into space. Bill Gates would not be able to donate the millions and millions of dollars that he donates to different non-profits every year.
There are a lot of good people with insane amounts of money that do many many good things that the government would never do. With an income cap, there's no incentive to push beyond a certain level, causing a stagnation in many fields, including medicine and technology. We would be outpaced by China, Japan, Mexico... hell, we'd be outpaced by North Korea.
There are a lot of valid and important reasons why an income cap is a terrible idea. And a government funded minimum income is just as terrible an idea.