This is one of those a classic “animals in zoos are sad” photos. Apes and monkeys are easy for humans to empathize with, and seeing one in a cage is hard to see without thinking of how it would feel for ourselves to be in a similar situation. It is very easy for articles to use photographs like this to illustrate their “get rid of all the zoos” articles.
This siamang was in the cage for ten whole minutes. They are trained to go into the cage so the keeper can get onto the island and keep things clean. I watched him row is boat over, reward the ape for getting into the cage, then walk the island picking up the litter that had fallen into the water and washed up to the shore. Before and after the visit, the siamangs were happily cavorting on their ropes and swinging all over the island. It would be nice to see them living happily in their native forests, but so long as humans continue to consume palm oil and coffee, that will not be an option.
For now, they’re living as happy lives as the world allows. Much like the rest of us, really.