If you need a tool to quickly draw a diagram, definitely check out Excalidraw. It supports the basic shapes and connectors for quickly sketching an architecture diagram, allows embedding images and even web embeds. It also has a nice integration with Mermaid, allowing you to convert flowcharts, sequence diagrams, and class diagrams into beautiful, faux hand-drawn diagrams.
And of course, there is an AI-powered text-to-diagram feature.
Maybe the most impressive feature is its real-time white-boarding capability: by just sharing a link to your current diagram, you can work on it collaboratively with a team mate or friend. Really amazing.
I heard about this in the (German) programmier.bar podcast - thanks for sharing, Sebi and Fabi!