It's true, pretty much. We developed configure scripts and ways to generate them in the days of 28.8kbps modems and they had to work on Unix System III and Xenix and HP-UX. We couldn't assume anything like Perl or Python was available. Linux distros were only just appearing, and there were no package management systems. Windows was still a 16-bit DOS shell. It was a different world. I'm amazed this stuff has endured as long as it has with so few changes. By the time Automake was written, several years after Autoconf, we at least felt we could assume the presence of Perl.
Want to know why it's called "Autoconf", which I think is a bit ugly of a name? I wanted to call it "Autoconfig", but when you add a version number and ".tgz" to that, you exceed the 14-character file name limit of some of the Unix variants it had to be downloaded and installed on!
Autoconf's main developer