for example if you're using Tailwind CSS or other CSS frameworks you can use this plugin to remove unused CS

Are you sure this is correct ? From what I see, the plugin (and critical npm package specifically with settings used by a plugin) is taking critical-path (above-the-fold) CSS, in-lining it into HTML and changing any link[rel=stylesheet] to link[rel=preload] to make page render faster (without waiting for css download). But CSS chunk is still the same i.e. contains unused CSS and to remove that PurgeCSS or similar solution is needed....

I mean, the plugin is great for page render speed-up but it doesn't remove unused CSS as anounced...