I don't think there's anything wrong with what the artist did; I think the problem, on the other hand, is expecting a lone artwork installation to make an entire space under the Gardiner inviting. It takes a lot more than that. The area under the Gardiner there still looks very bleak and not somewhere most people would have any reason or desire to spend time. That could change, but it's going to take some investment on various faces-- the ground plane landscaping and programming, the vertical features, the "ceiling" formed above.
Plopping an artwork down in a dead zone won't make it an inviting space. You just end up with an artwork in a dead zone.
A holistic approach to reimagining a space is what will ultimately lead to the space being more than just the sum of its parts.