I find that choosing when to pick is one of the most important decisions the winemaker has to make. I don't think there is a set brix level, because the answer is that it depends. It depends on the style of wine you are shooting for, as well as seeing what the vineyard can produce for you.
I've read that grapes accumulate sugar to around 24 brix, any higher after that is due to dehydration. If we have vines that are struggling to fully get to the brix level, we will drop fruit and cut irrigation.
In the end, I think getting to know the vineyard and getting the best fruit that it can give, then making sure it produces the best wine it can make, is the winemaker's responsibility.