By what measure did they consider Ada "too immature" I wonder? It's one of the oldest languages, an open international standard, and has been through several major updates over three decades. On the surface there are few if any languages that claim more maturity than that.
There's essentially just the AdaCore implementation that costs $$$, the GPL'd AdaCore implementation that requires you to publish your source code (because of the libraries) and then there's some unsupported GCC implementation.
I like Ada, and I would like to see it gain more market share. If it had, things like Rust and Go may have been superfluous. But the way things are, I just don't see it happening. Unless you're some big enterprise Ada is essentially a non-option, due to licensing, and if you're a big enterprise it's essentially a non-option since there's very few devs around for it. And so it remains an obscure language used in very niche applications (albeit with great success there?).
dons asbestos pants in expectation of anti eclipse comments!
Both Ada Core and Atego provide IDEs.