C genuinely is easy to pick up. It is harder to master. And you're right, for many domains, there are better options now, so it may not be worth while mastering it.
Because it's an old language, what it lacks in built-in safety features, is provided by decades of very good surrounding tooling. You do of course need to learn that tooling, and choose to use it!
In the context of Magic Lantern, C is the natural fit. We are working with very tight memory limitations, due to the OS. We support single core 200Mhz targets (ARMv5, no out-of-order or other fancy tricks). We don't include C stdlib, a small test binary can be < 1kB. Normal builds are around 400kB (this includes a full GUI, debug capabilities, all strings and assets, etc).
Canon code is probably mostly C, some C++. We have to call their code directly (casting reverse engineered addresses to function pointers, basically). We don't know what safety guarantees their code makes, or what the API is. Most of our work is interacting with OS or hardware. So we wouldn't gain much by using a safe language for our half.
I feel like this is a bit of an https://xkcd.com/2501/ situation.
C is considered easy to pick up for the average user posting HN comments because we have the benefit of years -- the average comp sci student, who has been exposed to Javascript and Python, who might not know what "pass by reference" even means... I'm not sure they're going to be considering C easy.
Honestly, C seems to be one of the easier languages to teach the basics of. It's certainly easier than Java or C++, which have many more concepts.
C has some concepts that confuse the hell out of beginners, and it will let you shoot yourself in the foot very thoroughly with them (much more than say, Java). But you don't tend to encounter them till later on.
I have never said getting good at C is easy. Just that it's easy to pick up.
Just to provide another data point here... that C is a little easier to pick up, today, than it was in the 1990s or 2000s, when all you had was the K&R C book and a Linux shell. I regularly recommend CS50x to newcomers to programming via a guide I wrote up as a GitHub gist. I took the CS50x course myself in 2020 (just to refresh my own memory of C after years of not using it that much), and it is very high quality.
See this comment for more info:
Having a good, logical description of supported features, with a warning that if you do unsupported stuff things may break, is much more important than trying to define every possible action in a predictable way.
The latter approach often leads to explosion of spec volume and gives way more opportunities for writing bad code: predictable in execution, but instead with problems in design and logic which are harder to understand, maintain and fix. My 2c.
