Being a person who doesn't typically want to draw diagrams, I opted to go with draw.io as it looked very simple and easy. However, I was nudged to try PlantUML and to my surprise it was a lot simpler and faster to create diagrams. A point which you mentioned is maintaining the diagrams for long-term. We have a docs folder in our repository which includes all our PlantUML. It's quite easy to pick up as a language, and because it generates the diagrams for you, you don't waste minutes fiddling with getting the arrows all matched up. I would definitely give it a try - makes life so much easier!

Plus, there is a VS Code extension for it as well, which auto generates the diagrams when you save.