One side likes high skill immigrants but does not like low skilled immigrants. The other side likes low skilled immigrants and thinks high skilled immigrants are a-ok too. To try to get their way, the low-skilled side says we won't pass your high skilled stuff unless you pass our low-skilled stuff. The other one refuses and you have legislative deadlock that prevents changing much of anything.
That's what I've heard about the problem currently.
Also I wouldn't base it on federal taxes, because people with state taxes will pay less federal tax since the state tax is a federal tax deduction or similar. I would base it on total USA tax load.
If you're paying $30000 in income tax every year, which would be lost if you had to return to your home country, there's a really good reason to just hand you a green card. $30k is a significant chunk of a useless government sinecure, after all. And if you make it based on taxes, you can be reasonably certain that it will be recurring revenue, rather than a one-time windfall. And at that income level, you're likely to be a high-expectations parent to a child who will eventually speak English and want to stay forever. So bring the spouse and kids!
As a nation, wouldn't we want to encourage as much immigration as possible from people who will be net contributors to our society? Wouldn't we want to bring their families with them, so they wouldn't be remitting their earnings back to another country? Ignoring all the irrational racism, of course. That might still be a problem.