I agree. Depending on the climate, it can not always be possible to house a species in it's natural environment, but consideration of animals, keepers and visitors should be considered. Often I find that an exhibit has too much foliage etc,. for the animal to be seen clearly. Good for the animal, but not for the visitor, who pays to actually view the animal.
Agreed. Species like Polar Bears and many desert species are often housed in temperatures higher or lower than they would normally experience. Though this does generally cause issues replicating their natural environment. Ice and snow are restricted to enrichment in warmer climates for the bears because it is typically not feasible to provide it. (I did see that San Diego has a snow machine incorporated into their Polar enclosure, though it covers a tiny fraction of the exhibit in snow.)
Foliage is commonly in the way of the guest's viewing to some extent or another, but at the same time the plants are often serving as visual barriers to the animals, either from each other or guests. Frequently I've seen animals disappear into more vegetated areas of their exhibit when loud guests or other loud unknown noises are close by. Highly beneficial for the animals, but frustrating for the guests, and likely the keepers too, especially in larger exhibits. However, that privacy for the animals suits them far better than concrete and iron bars. No matter what, there are always some animals that will not be seen in a zoo on any given trip. Frustrating for us as guests, but the animals are far better off with that added privacy.
I think zoos should do their best to replicate an animal's natural environment.
Most (if not all) of the reputable zoos do try and replicate the native habitats of their animals. Though I think a difficult factor is some species often prevent full replication of their natural habitat due to behavior. Elephants in particular come to mind, I think only once have I seen an elephant yard containing trees or bushes (and the trees were hot-wired in that one, can't seem to remember what facility that was...) They are simply too strong with a big appetite for greenery, typically resulting in a lack of vegetation in their areas. Similarly, when I visited the San Diego Zoo a few months ago, in the new Hamadryas Baboon habitat I noticed a large number of plants the baboons had dug up and strewn about. In many cases species tend to be pretty rough on attempts for a naturalistic exhibit.
On the other hand, some animals will not survive if their exhibit is not pretty close to their natural habitat. Emperor Penguins require freezing temperatures and cold water. Deep-sea animals typically need low lighting, cold water, and a good amount of pressure to survive.