The previous mess of languages didn't provide the features that were specified as requirements for Ada either - effectively, the previous languages were heavily

The previous mess of languages didn't provide the features that were specified as requirements for Ada either - effectively, the previous languages were heavily "first few generations of programming languages", often arcane and with limitations related to platforms that were no longer dominant. JOVIAL which was one of the major ones (even standardized) is essentially a slightly updated (using features like structures) ALGOL 58. Then you have tons of various assemblers. TACPOL. There was a gap for a modern, safety & reliability oriented language - and which could be used to unify the mess that existed before.