Countries should vet who they let in. They shouldn't blanket ban a country because of its leaders' policies, or else pretty soon US citizens won't be able to travel anywhere due to global disgust with Trump's bozocity.

I've heard lots of complaining about the ability of the rich to effectively buy visas.

As for why? Because this blanket ban is not useful, it violates the spirit of religious freedom, and it's going to cause a lot of real harm both to people who want to come here, and to our own country due to excluding people who will make us better.