I don't know what kind of engagement could come from a channel trailer, since it's a creator-to-viewer experience. Kind of saying, "Here's my channel, please check it out," but not something that would engender much discussion. So engagement wouldn't be a big deal.
I was just at a YouTube Creator Day and I can't remember the percentages, but channels with a trailer did better by calculable percentage points than those without, especially for unsubscribed views. So it's definitely something that works for Youtubers-at-large. On a creator-by-creator basis, I'm not too sure how that works out, but it seems like if it's something that is, on the average, beneficial to a channel, it's worth trying.