Your instance is defederated from sh.itjust.works (and a lot of others). You can’t access anything from sh.itjust.works from your instance so you either need an alt account or just switch instances entirely. If you need a new/additional instance sh.itjust.works would be my suggestion
It is open source and on the Mozilla store, did you get the right one? The idea is that you whitelist the websites you trust so only trusted sites can execute js. A lot of websites have js free alternatives like libreX/Y instead of google. There also is GNU librejs which only disables js that doesn’t show its source code. It being a main component of the tor browser tells you a lot about the threat level it’s for. As I understand it the difference to ublock is that it’s lists are on a “allow all but” basis and noscript is on a “block all but” basis.