If most of the potential users of the UA forum felt as you do, it would probably be time for a split. The split you suggest is the most logical way to do it. At some point that will be what happens, unless filtering tools become available in the meantime. The question is whether now is the time.

What makes this so hard to decide is that the current users of the forum probably prefer it the way it is. People who find it unusable have already left, or never stayed after their initial visit. Therefore we have to guess whether the change would increase or decrease the value of FT to future users. If a substantial percentage of current forum users (meaning the people who didn't give up and leave) is in favor of a split, I would find that persuasive.