I think the other reason non PHP devs think we are in the dark ages is because when they google it, our documentation looks like it's from 2010. It's a bit of a joke really.
One other thing I always found iffy is the comment section. Why is the information there not reviewed and back-ported into the documentation? Sometimes, as on the page of the `DateTime` class, they actually contain crucial details!
I wonder if that's somewhat on purpose. Part of the remaining stigma with PHP is that people cite bad PHP examples from WP.