So it solves 2,3, and 4. Can do Pacific. Cheaper to operate. Can be used on all overseas routes.
Wiki says: The overall thermal efficiency of the engine in supersonic cruising flight (supercruise) was about 43%, which at the time was the highest figure recorded for any normal thermodynamic machine.
https://en.wikipedia.org/wiki/Rolls-Royce/Snecma_Olympus_593
The SR-71 was not exactly manoeuvrable or efficient at low speeds, its efficiency range was above M3.
There aren't a lot of supercruise aircraft out there. The F22, for instance, can supercruise effectively, but the F35 cannot.
The Concorde only needed afterburners to get to speed and altitude. They did not use afterburners for supersonic flight at altitude.
According to someone on the talk page, the Concord's engines acted as ramjets at high altitude.
Wiki again: Forces from the internal airflow on the intake structure are rearwards (drag) on the initial converging section, where the supersonic deceleration takes place, and forwards on the diverging duct where subsonic deceleration takes place up to the engine entry. The sum of the 2 forces at cruise gave the 63% thrust contribution from the intake part of the propulsion system.
https://en.wikipedia.org/wiki/Rolls-Royce/Snecma_Olympus_593
I remember reading a book by an engineer from the Concorde program (he's from the UK) who got invited by the Americans working on the B-1 bomber (which was initially supposed to be a M2.2 thing).
They wanted to exchange about air intakes problems such as efficiency, surges, and all. The author was not impressed at all by what had been developed and tested on the B-1. And he thought what they had on Concorde was so much more advanced (he might have been totally biased of course).
Because as people say, Concorde was not tested, it was developed (hence the many prototypes, pre-production and first production models) because a lot of the technology had to be created and if it didn't, it had to be modified to be usable on a civilian aircraft.
A classic example is pulling the throttle all the way back while at full speed: on most fighter jets of the era, you'd completely trash the turbine if you did that. So they had to create a plane which did the right thing for pilots who weren't trained like fighter pilots...
It was also a case of doing all the wrong thing in terms of management. Like assembling two of the same things on each side of the Channel to please respective governments...
The Concorde was capable of supercruise.
Still, we have had a few years of engine technology improvements since then.