I would challenge that it is slow this way. There are plenty of catamaran sailors in the top of any fleet that have rudders or daggerboards that make some amount of noise. A bit is careful work on trailing edges and making sure that leading edges do not have some kind of snag will eliminate most of it. But consider this, with the noise you have an idea of whether you are going fast or not. If you are sailing along and the boat is making all kinds of racket then all of the sudden it is silent you know immediately that you should make some adjustment, right? For someone who is not on their boat all the time this could be the best way to know if you are keeping the pace you need to the whole time. It may not ne a bad thing. A little noise is not a big drag on performance.

Later,
Dan