The compilers were dead slow.

Ada was ahead of c++ by years, but it was unusably slow in compile debug cycles compared to c++.

http://archive.adaic.com/intro/ada-vs-c/ada-vs-c.html

> The compilers were dead slow.

And also expensive.

Nvidia recently chose Spark/Ada for some of their safety critical software.

https://blogs.nvidia.com/blog/2019/02/05/adacore-secure-auto...

It's still used in defense and aerospace. Last talking to people who were making inertial navigation units (the movement sensors like in your phone but much better and for a plane), all the software was done Ada, millions of lines of Ada.