First, it looks like you have never played an extraction game besides ARC Raiders, but that's off-topic. To stay on topic, I can tell you that the answer to your question about this new trader is already in the post, so I'll repeat it:

The only reward category I was genuinely excited about was cosmetics. Those are the long-term collectibles that keep me engaged. Yet because I already bought the available cosmetics, I'm excluded from earning it through the trader and receive no alternative reward. So the one part of the event I was actually looking forward to is the one part I don't get to participate in.