I will just offer my opinion here, but I will admit this is not my area of expertise. My understanding is that there many complaints within this platform and many others about animals walking thru everything and anything. It really did take most of the realism away from the game. I do agree that the current hit boxes of certain animals, are too large, however I do believe that they have stated already that there is nothing that can be done with what they currently have to work with. They have also stated that they will continue searching for a solution, it is the best they can do.
As far as creating extremely detailed and realistic animal habitats, it is certainly more than possible with the current format, you might have to push creativity a bit further, but it is far from unattainable. As you have mentioned rocks and foliage being the problem, I did design an exhibit a while back, somewhat unrealistic in size and scope, but the idea and purpose was to test traversable areas in Planet Zoo for all animals. The design follows the concept of a thematic animal park I have been planning on building. Every single animal with the exception of the African and Asian Elephants were able to move completely around the exhibit, I did have to make some alterations for the Giraffes, Hippos etc, but it was nothing major. In short, after my short experiment ended I honestly can not see how this is such a recurring issue for so many.
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