Here's my two pence on why I think Titboo was so loved.
I think the simplicity of the map is why it was so popular. It was very basic which put the focus on "teamwork", outwitting the Dragon and using Mr.Saturn.
A lot of the other maps had layouts that kind of alienated those aspects. It made things unnecessarily "complex" which took away from "teamwork", outwitting the Dragon and using Mr.Saturn. Its kind of hard to put it into words but things like excessive amounts of branching paths and lots of areas where Pigmasks could drop down from made it hard to keep focus on the simple goal.
I wasn't a UCH wonder by any means but when I played as Chimerea on maps like Headqaurters and Titboo it felt like I could plan my next actions within moments just because I could quickly analyse which areas a Pigmask could attack from. Of course this didn't make me invulnerable by any means, a quick distraction or a Mr.Saturn to the head could easily result in my downfall.
What I'm trying to get at here is that in my opinion the reason Titboo was so liked is because it was simple and flat. Which put the focus on gameplay mechanics and teamwork rather than map knowledge and areas of attack.