This is a great list, and it's good to see a counterpoint to the autobashing that's trendy these days.

One additional point: autotools are bootstrappable without going all the way up to C++ (CMake, ninja) or Python (meson).

And yes, muon and samurai are written in C99, but as soon as I wanted to both support -fvisibility=hidden and unit tests in my project, I was forced to build both static and shared libraries. This forced me back onto libtool, and once I was there I figured I may as well stick with the good ol' autotools.