Concorde was almost coach level cramped. There is no way this will be as comfortable as top end subsonic lie flat business or first class. For 3h vs 6h that doesn't matter. For 7h vs 13h I assert it does.

In a number of ways, modern upper class air travel is significantly more comfortable than it was throughout most of the Concorde era. First class and then business class were a lot more like today's domestic first/business class even for long haul international flights. Of course, things like entertainment options are a lot better today as well. (Though there's no 747 upstairs first class lounge :-))

Security, etc. is worse of course--though that's largely outside of the airline's control.

So was Concorde, but they were very uncomfortable (been on a couple in museums). Concorde feels like coach in a small commuter plane.