I think that’s quite unfair. You’re grossly underestimating quite how much hard work would have to go into defining that transaction system, working with the connecting parties to agree how it will work, then building it, then getting it accredited/approved by regulators, then launching it, then scaling it, then providing support for it, then providing customer service for it, then changing it when regulations or other peoples systems change, ten changing it again as new features are needed, then rebuild it every few years as dependent technology goes out of support and thus end of life, etc. The list goes on.
Software and systems are not just build it and then do nothing things. They’re incredibly complicated and require the full-time commitment of dozens, sometimes hundreds, sometimes thousands of people to make it a continued reality.
The people that make transactions between banks happen, are not doing nothing, not by a very, very long shot.