I think each country sets their immigration policy in their own self interest. China has obviously decided that keeping Covid out of China is more important than having businesspeople from other countries visit (not just the USA, this policy applies to every country in the world). The USA thinks it's worth keeping itself open to visitors with visas, as is its right and to be honest the USA doesn't have much worry about foreigners causing more covid as they have a let it rip policy domestically.
People can complain all they want but the policies are based in self interest on both sides.