That's not quite true. The fact that other Unity games are working just fine indicates that there is something that can be done on the part of the developer to make Unity engine games work in fullscreen with El Capitan and NVIDIA cards. Wasteland 2: Director's Cut runs just fine.
I could be wrong but, since no one will elaborate on this issue or really explain what is going on, I have no way to know that. Thus, with the information I have at my disposal, I have to assume that there is, in fact, something that Obsidian can do to fix this. If someone has information that contradicts this assumption, please share it with me.