To be clear, there is no ban on tourists. In Amsterdam, anyone over 18 can legally buy weed and hash at the coffeeshop. And everyone will be welcome to hang out in the coffeeshops again once the measures against coronavirus are lifted.
The coffeeshops are open, but currently only for takeaway and only until 20:00.
The mayor of Amsterdam did propose to ban foreign visitors from the shops, and who knows how far she will get with her plans, but for now, we are just waiting for the lockdown to end and normal life to resume.