As I posted, many of this issues was problems of materials and technologies of it's time. At start of Jet engines and jet aviation it had exeact same problems: too much cost, too low resource of engine, eat many fuel. It requred a lot of years to make them profitable. Experiments with it was even in 20s, but first commercial jet planes started developed in 40s, and only in 50s DeHavelant Comet appeared, and it more fail that victory considering how much problems it get and same as supersonic jets at one point was just closed after some crashes. However, because it, Douglas DS8 and Ту-104 and Boeing 707 that came after can avoid most of this initial problems, but even this, 2nd generation of civil jet planes not lived too long to be replaced with much better ones only after 5 years or so.
Not all of problems of supersonic planes are resolved, but they much, much more technologically now. Even 80s projects that no did it because - like Ту-244, was already in many ways more rentable and logical. Only 10 years after first generation, was already created technologies that might make this planes much more sucsessfull. This what I said in previous post - ew electronics, new engines, new materials. If supersonic jet projects of 80s did it, they'd had no this overcomplicated moving nose on landing, have less requrements and less personell for piloting and maintain, have bigger resource and was silent, but in 80s nobody wanted it because marcet and politics and initial dissapointment and hype about wide-body planes.
However already in 90s boeing re-started someprojects, like this boeing sonic cruser. This plane meant to be fly on trans-sonic speeds. Project was mainly cancelled because events of 9/11, problems in market of civil aviation afterwards and all related shit. At 2018 most problems with such projects just as many because they started not as good as original first jet planes did and everybody fear to loose money on something new, espessialy big companies. But small companies with big corporations behind them very actively working on supersonic buisnes jets. This is segment in which market most shure, since small buisness jets most probably be even more cost effective and less dissapointment if they fail than if full scale large, multi-passenger aircraft did so.
Like this Aerion SBJ I talked about - very promesing and in many ways very fresh conceptualy project. Well, fresh for civil planes, but already known for military aviation. This trapezoidal wing, back engine arrangement, most modern aerodynamics, most modern materials and technologies and allso not very big scale of plane will reduce problems of sonic boom to minimum. Giant of Lokhed Martin behind this samm company and they promesing that project more or less be done in mid 20s and first supersonic buiseness jets appear at companies service. I belive that this time it is most safe and guaranteed sucsess, and after it bigger variants will be only question of "how soon". I so shure about it because as I said already, supersonic jets already may be sucsess in 80s technologies, and we now far ahead of 80s.