Unfortunately, font-variation-settings isn't supported by Firefox, Safari, IE, or older versions of Edge, so these settings only work for ~70% of users according to Can I Use.
It was a bit frustrating viewing this site on Firefox and not having any indication of why the settings weren't changing anything.
Of course, maybe that's because there hasn't been enough demand for it, and now that there is a font that's widely available which can use this, Firefox might finish enabling it (looks like there is a flag for it, but it's not enabled by default).
Support for font-variation-settings has been on by default since Firefox 62, which was released almost two years ago. Are you using a Firefox older than that?
Ah, sorry, I was looking at the wrong item on "Can I Use...", @font-face: font-variation-settings, rather than the "Variable Fonts" item which covers font-variation-settings outside of @font-face rules.
It was a bit frustrating viewing this site on Firefox and not having any indication of why the settings weren't changing anything.
Of course, maybe that's because there hasn't been enough demand for it, and now that there is a font that's widely available which can use this, Firefox might finish enabling it (looks like there is a flag for it, but it's not enabled by default).