It's maybe 80-90% of the way there, depending on what you need. Closing the gap feels demoralizingly hard with no resources (I'm spending time on it unpaid).
The design environment is quite complete, although it doesn't even try to expose all of CSS -- instead it's more like a "walled garden" of the parts that make sense for mobile-first designs.
I'm most proud of the exported code's quality (no extra junk, no giant library hanging around) and also the component and plugin architecture. You can either design React components visually or import them from code (e.g. an npm package), and both will work the same within a design.
The fundamental problem is that the technological foundation for web apps is so unsuitable, like building a house on quicksand using decayed planks. CSS is a cruel joke with its thousands of properties, their decades of cruft and their unpredictable interactions. HTML was designed for documents, then was semi-accidentally turned into a view layer, but it never adopted any of the learnings from the successful '90s GUI desktop frameworks. Some of that missing structure has been added back by efforts like Angular and React (and the latter is fine to my taste), but it's just really frustrating that web front-end development is still stuck endlessly patching over a rat's nest of <div>s into something that resembles actual UIs. But what can you do? It's not like browsers are going to add a real app framework. So here we are, still trying to decide whether buttons should be <a> or maybe <input> elements. Sigh.