Not at all, loofah - a lot of the older generation (like my own parents) stayed together because they had no option, they didn't want to be together but it was not the done thing to separate - and extramarital relationships were frowned upon, so they were unhappy, like it or not.
I'm not convinced that multiple partners make anyone any happier, it means people don't have to work at relationships any more, they just up and go when they've had enough, there's no staying power in some relationships these days - and I do speak from experience, I've been married twice, the first time much too young.