The new UI in SourceTree 1.8.x is a MAJOR dealbreaker to me and countless other users. Yet some people (presumably aliens whose vision works differently from that of humans) seem to like it, and for some reason the dev team seems committed to keeping it.

So why not let everyone have their way and support skins/themes? This would be a major general improvement to the app, besides the obvious advantage of ending this "war of religion" between old an new UI. Those who like the old look can keep it, the aliens can keep the new one, and creative contributors can design new and even better ones. Everyone wins.