I created a no-code tool that could do joins, filters, and more with GraphQL, so I really don't see your point. You just need to do it a bit differently (same as REST, and if you follow REST 100%, good luck with n*m calls when you want to join two resources that you don't know from the start):
GET clients [client 1, client 2]
for each client
GET business (id = client.id)
Now think you can join with business, jobs, invoices, employees, etc etc, and tell me how to do this in rest without basically recreating a query language?