Same [1]. Zoom being outsourced to the implementing platform is one major pain-point. That example from us has grown in size.
Having to bump the processing limit multiple times for mermaid to not refuse processing big diagrams, using touch zoom gestures on the laptop, because the diagram is so small, that browser zoom can't provide enough magnification, the list goes on.
We are clearly using the wrong tool for a diagram of this complexity, but the practicality of seeing commit changes in the diff, what property was changed by whom and instantly having the visual feedback in the Pull Request is just way too useful to switch to a "proper" tool.
However, it doesn't scale very well past a few dozen elements (in terms of layout and display). Not sure what other's experiences are like?