"The best camera is the one you have with you" is a good adage. For prototyping a language needs to feel effortless so you can deal with the essential complexity of the problem and not hesitate to jump in and experiment.

For implementation, it's whatever tool best fits the job.

C is a good compromise, but it requires real discipline. The CPython and Linux code bases are great examples of how C can be wielded well in practice. But of course C also famously offers unlimited opportunities to make a complete hash of things. I certainly wouldn't recommend it to anyone as their first and only language.

An alternative approach is to be bilingual. For my current project the final code is in C++98 - sometimes there's no good alternative. But I do most of my experimentation, tooling and prototyping in Python. Python's excellent C/C++ interoperability is a huge benefit in this.

I definitely agree with the article that you shouldn't avoid hard things that improve you. But in choosing between ADA and C, the right answer is both and neither.