Thanks! I took a look at the plugin, and it looks very simple. The problem with CartoCSS is that it doesn’t do styling in layers like QGIS, but in cascaded properties.
So instead of taking a style and drawing all relevant objects, CSS takes an object and figures out what the style should be.
Translating from one to the other is a royal pain, and that’s why my plugin already took 2 weeks of work and still isn’t done.