Bitcoin future mass usage for payments - how feasible is it without real privacy
Bitcoins themselves are fungible, and addresses are designed to be for one-time-use only. It really comes down to how you use it, and it is entirely possible to transact using Bitcoin in a private manner. 

If the user is naive and has poor practices, then it is possible to track their financial history.

But if the user is smart and uses best practices (no address reuse, coinjoin/payjoin transactions, lightning network, etc), then they can enjoy a very high degree of privacy, and sovereignty (you don't get this with traditional banking). 

This article is a great writeup about privacy while using Bitcoin.