I mean firefox's built in pdf reader is PDF.js. Also the desktop version of adobe reader used to run javascript embedded in pdfs by default as a "feature". I'm not sure you can get away from it at this point, but it would be nice to have the option to just use a desktop pdf reader that doesn't even support javascript or running any code embedded in the pdf. Maybe my use case is limited but I don't see the point of it. If you want interactivity you can use a website so people can expect that sort of stuff.
