Agreed that Sphinx is extraordinary and wildly underrated. Sphinx is the only architecturally sound, extensible, widely used documentation framework that I know of. Its plugin ecosystem is amazing and gives me incredible leverage to improve documentation for teams and projects.
I'm not a fan of reStructuredText, but nowadays it's possible to do most things that previously tightly coupled Sphinx to RST in Markdown, courtesy of MyST-Parser: https://github.com/executablebooks/MyST-Parser
Except that the plugins are not compatible with each other or the latest version. That means I'm seeing some bugs that are fixed in the latest but I can't get the fix because my doxygen plugin doesn't work with the latest, and even if it did is the mermaid plugin updated yet? (please don't ask which versions of each I'm using - I believe there are at least 2 different ones that can do both of the above and they all have different abilities...)
I'm not a fan of reStructuredText, but nowadays it's possible to do most things that previously tightly coupled Sphinx to RST in Markdown, courtesy of MyST-Parser: https://github.com/executablebooks/MyST-Parser