Well for non-developers it’s actually less of a hurdle if it’s just java. I’ve thought about using electron or similar, which don’t need java, but they have a huge weight (above 100MB download for a hello world, which is even less acceptable). There are java executable wrappers, which remove the need for java, but I don’t think they’ll improve the size problem much.
So I’m guessing the only solution for you would be an online service.
One alternative to Java or Electron is a Web Extension backed up with a node.js native app to provide the missing APIs. The native app can come with its own installer, whatever the platform, and it weights ~ 30MB. This is the solution i chose for my add-on.