But lets be clear, people who either cheat or set up open relationships aren't really wanting to be with the person they are with... that person is just the best they can hook for the time being. That seems rather depressing to me.
No, people who set up open relationships aren't "really wanting to be with the person they are with" exclusively.
And people cheat for all kinds of reasons, it's not for someone else to declare that they don't want to be with the person they married or whatever. This stuff always gets presented as black and white which is neither helpful nor true. I know people feel good about themselves declaring what they wouldn't put up with and how horrible other people are but it is easy to do that.