I think the decision to have no live plants in the animal spaces of Tropic world was pushed by the Zoo's vets and curatorial staff, who wanted a pathogen-free, "hoseable" environment. It's ironic that at the very same time, Woodland Park was creating a living forest for their gorillas. Tropic World initially only had a few skylights, on the north side of the building, so growing plants might have been impossible even if the animal managers had allowed it!
Habitat Africa: the Forest is not a whole lot better than Tropic World. A few more living plants, but mostly concrete, epoxy and fiberglass, in a very dark space. I was disappointed to look into their duiker exhibit and see an ugly green bathroom rug set underneath a concrete earthbank. Until I realized this was the only "soft" piece of furnishing in the entire exhibit--the poor duiker needed something comfortable to lie down on!
I forsee better things ahead for Brookfield though--several of their new top management came from the Bronx/WCS, and understand how lacking the current facilities are.