Now I'm curious... What did the treefolk do to you?
My cube was initially super low powered, so they used to be arguably the strongest tribe if you had the pieces and most of them were also warriors or shamans and played well with elves. This worked because the cube used to play like durdly kid magic at first (which was really fun for a while, especially as some of my players were kind of newbies at that point so a tribe of 3/6 looks really cool and intimidating). But as the cube grew more focused and powerful, treefolks had a hard time keeping up (there is sweetspot for them at the same level of play that allows
this, but my cube was moving on). They are a costly tribe, with worse bombs than giants, and worse midrange potencial than beast. On top of that the monogreen player loved elves so in the end the only treefolks that really saw play was these guys (plus reach of branches)
They had some crossover with black, but elves were better at that too.
Doran is a great card but you have to splash white for it, and white has no good treefolks. There are a bunch of other reasons as well, but it concerns other parts of the cube that are not really related to treefolks other than incidentally or through competition of slots.
I might go back to a lower powerlevel at some point, or if wizard decides to print some good low cmc treefolks and some good white treefolks then they will come back. Right now I am trying to see how far I can push the powerlevel and still keep tribes viable/fun/synergistic and in a singelton format.