I like excalidraw for live discussions but if I want to make more detailed or better looking diagrams, I really enjoy these two tools:

- For drag-and-drop/WYSIWYG, I really like DrawIO. They have a web version https://app.diagrams.net/ but I strongly recommend the desktop version https://github.com/jgraph/drawio-desktop/releases/

- For text-as-diagram, I think Mermaid wins this by default since GitHub added markdown support for these: https://mermaid.live/ (This was github's announcement https://github.blog/2022-02-14-include-diagrams-markdown-fil... )