Sirio did swap to aluminium with their .21 carbs and did solve some issues. Isn't it just that today a milling machine and a piece of aluminium is much cheaper than a plastic molding machine?

The most crappy carb I have ever seen was the old Mega P5 carb, it had always trouble finding the right adjustment without hick-ups or jiggering. Most people did seal anything off with a kit or special sealing paste but finally the needle was the cause, you had to shorten it. I think there are many other things on a carburator making a carburator good or bad.....