My main diagramming tool is Microsoft Visio, but I also use Excalidraw and AsciiFlow when "sketching" rough ideas. I create architecture diagrams - these show

My main diagramming tool is Microsoft Visio, but I also use Excalidraw and AsciiFlow when "sketching" rough ideas. I create architecture diagrams - these show how different components fit together, what network boundary they reside in etc. I like Visio for these in particular, because I can use different images to represent each component - I find it makes the diagrams easier to read. I create "security diagrams", which are basically just a box for each significant component, with lines and arrows showing the direction of network communication and what protocol and port are used. These diagrams also show what kind of authentication is used. I create use case diagrams, to show the actions that different roles within the system can perform. I create very basic inheritance diagrams only to show different roles within the system. I occasionally create action diagrams, if needed to help understand decision flows. I occasionally create sequence diagrams, if needed to help understand the sequence of interactions between different components/modules/actors. I very rarely create class diagrams - if I have to do this, it basically means the design is too complex (e.g. too much use of generics, too much use of inheritance etc). UML is far from dead, it's just that people don't doggedly churn out and maintain every kind of UML diagram for every part of every system - they are really useful for explaining a few specific parts of systems.