[WorldMaker]

The direct relative tool to javadoc/docfx is Typedoc [1], which this tsdocs.dev hosts (a fork of). The benefits tsdocs.dev adds on top of Typedoc are the ability to open any arbitrary npm package (plus some smarts for @types/ package redirects) inside a hosted Typedoc whether or not that package's own docs site includes a Typedoc view or not.

I use (Markdown plugin versions of) Typedoc output in some of my packages' docs sites. It is a handy tool and I know some users appreciate having it built with the other docs. I'm also personally equally likely to jump directly to a declaration file rather than pull up a documentation site, but I appreciate things like Typedoc when I do find them on other projects' documentation sites, and I appreciate tsdocs.dev for giving a way to further do it for arbitrary packages that don't include it, even if in many cases that won't be the first tool I use for the job because I'm comfortable enough directly in declarations files.

(Also, you mention a good decompiler, its important to remember that Typescript declaration files generally aren't decompiler artifacts and may be inaccurate to the code actually running. I'm more likely to trust a package that generates its own Typedocs in their documentation as that implies they keep their declarations up to date and/or write their library in Typescript directly. In other sorts of projects for me sometimes the next jump from the declaration file is to the source files. I've PRed a lot of declaration file fixes over the years.)

[1] https://typedoc.org/