I'm pretty obsessed with diagrams as code and unfortunately while I liked the visuals produced by Mermaid I found some major limitations with it on my last comparison test a few months ago. I think it might just need to mature a little bit and then will probably be a solid choice. More of a greybeard sysadmin thing, but I usually refuse to install npm things locally so thats another issue for others who feel the same.

What I use myself and suggest to others these days is first and foremost blockdiag and its variants (nwdiag, seqdiag, rackdiag, etc), and the very descriptive python "diagrams".