Even disregarding climate impact (which we shouldn’t) it seems like supersonic flight is just the wrong direction to be going in. If the commercial aviation industry is to survive beyond a century or two they probably need to find a different energy source for planes.
Also, it’s just not like the train to plane transition where passengers experienced 5-10x average speed improvements. The maximum amount of time you can save for a round trip flight is about a day. There’s just a limit to how much value that has. Business travelers can work on the plane, leisure travelers can just take another day off.
I mean, speaking of trains, flights sometimes gave a hard time competing with those, too. There are a lot of situations where going a little slower isn’t a problem.
A few weeks of war in Iran showed us the impact of reduced availability of oil. The rise in the number of amplitude of climate events show us that a lot of what we do is not sustainable.