I bet the Kevin Conroy thing in part 3 is him just saying a couple of lines, a cameo...
Anyway, yeah this was bad. It's boring. Way too much screentime for Psycho Pirate's past which they should've used for other characters.
You can tell that it's cheap because the worlds are empty. (Plus the crappy animation of course) Also that preview clip they released is basically false advertising, that's not what you're getting at all.
Part 1 was a lot better than this, which wasn't great either... I really hope we get a reboot after part 3, I don't think I've really liked any movie of this current universe. They range from "bad" to "just okay."