Ada is only a solution if it can fulfill the project requirements regarding the libraries, tooling, supported CPUs, OSes and IDEs.

Sure. But now you're retreating to a rather small set of applications. Ada has nice tooling and supports a pretty large number of platforms. I don't think you'll find many niches where not one of Rust, D, Swift, Ada, Java, Go, or the dozens of other memory safe(r) languages could do the job and only C or C++ are adequate.

Practical example, we use C++ as systems language for projects done in Java (Standard, Android), .NET (WPF, UWP, Xamarin), Swift/Objective-C (iOS).

There isn't much Ada tooling available for those environments, and even using GNAT would be increasing project costs regarding having to implement ourselves stuff that we get for free with the SDK tools that support C++ out of the box.