A decade or so ago, I was tasked with auto-generating documentation, including diagrams (super- and subclasses, to begin with), of a fairly large system in a domain-specific language developed over the past couple of decades. The language had a kind of multiple inheritance (a traitlike system), and at the time around 1500 types/classes/traits/mixins/whatevers, with the entire system all queryable at runtime (and indeed that’s how I generated it—someone else provided Python bindings to the system, then I traversed it all in Python). Just to amuse myself, I generated one class diagram of the entire system. It was around 30 metres wide and I think 30cm high when I zeroed all the margins and padding I could in GraphViz. Flipping its orientation, I got it to be 15 metres tall and almost 1 metre wide. I figured it could be fun physical wallpaper for the office, but in the end settled for just a labelless rendering with random line colours as a desktop background. It was pretty.
But more seriously, it depends on how complex the system is and how it’s modelled. The case I was working with then transferred excellently to such diagrams (shallow and deep inheritance, and other forms of composition and linkage, with every box a link) and key-value property sheets about the types and the likes, but I don’t think I’ve encountered another system where anything even vaguely like that would work particularly well.
That's a great point, I doubt there can be one single modeling solution for all systems. I imagine a modern tool would be more like a suite with many options for common use cases. And it would be essential to be able to narrow down on specific subsystems maybe using something like a gitignore file
But more seriously, it depends on how complex the system is and how it’s modelled. The case I was working with then transferred excellently to such diagrams (shallow and deep inheritance, and other forms of composition and linkage, with every box a link) and key-value property sheets about the types and the likes, but I don’t think I’ve encountered another system where anything even vaguely like that would work particularly well.