But Ada had for a number of years a mandate to require its usage [0]. That should have been an extreme competitive advantage. And even then, C++ is still used these days for some US military projects, like F-35. Though I don't know whether the F-35 is successful or not, if it is not, that could be an argument against C++.

Ada is almost non-existent outside its niche.

The main companies arguing for Ada appear to be the ones selling Ada services, meaning they have a horse in the race.

I barely have any experience at all with Ada. My main impression is that it, like C++, is very old.

[0]: https://www.militaryaerospace.com/communications/article/167...

> The Defense Department`s chief of computers, Emmett Paige Jr., is recommending a rescission of the DOD`s mandate to use the Ada programming language for real-time, mission-critical weapons and information systems.

Poking around it looks like ada is actually the minority now. Everything current is either transitioning to c++ or started that way. The really old but still used stuff is often written in weird languages like jovial or in assembly.