I would somehow tax inactive capital. Capital that is not directly invested in a company or pays for employees. Everything laying around or on the stock market should be heavily taxed.

That doesn't change the ownership problem. This solution could still allow for a a handful of people to own everything because they would be invested in, and therefore have ownership of, all of the companies.

The stock market is for directly investing in companies...

Islam bans stock markets and interest (though not all current so-called muslim countries) and every person who is rich (who have more than 87 grams of gold worth of things) is obliged to donate %2.5 of their total wealth to the poor every year. In Muslim countries, the state collects and distributes this, so it's effectively a tax. Necessities of life (shelter etc.) are excluded from total value calculation. Muslim countries traditionally took away land of people who didn't utilize it for 3 consecutive years, though idk whether this is rooted in the religion itself.

That's probably state land and regular people are not allowed to own land. If they don't work it, it gets transferred to someone else.

Yeah, right iirc.