I understand how team rainbow is supposed to work, but considering the strong disagreement regarding it's use, I feel like they shouldn't be added. The idea isn't a bad one, because half of the community likes it, but without community consensus, the idea shouldn't be added.
For starters, specific differences between team underworld and team rainbow should be mentioned.
For instance, team underworld is all about the segregation of elements, and has to play a mono (but can play any mono), while team rainbow cannot take more than 10 cards from an element in their deck.