I have enjoyed using PlanUML, but getting a local renderer for team use is a big lift. I switched to Mermaid-JS last year. Using mermaid, we can do a number of diagrams in Markdown code blocks. VSCode has a markdown preview enhanced that can render these, and Gitlab will render mermaid. Also, you can get a mermaid plugin for Confluence.

It may not be the "best", but it's exceedingly versatile and has a low barrier to entry, which is a huge win for us.