No matter what media and blueball friends will claim relationships are not a place of good sex life. Sexuality relies on seduction and seduction relies on mystery, deception, imagination and novelty.

The only relationship it's kinda possible if couple does not co-habitate but even this will lead to boredom because people have big egos and get lazy. I often watch couples in park, they are dead bored. They think being together is exciting but it's not. Excitement requires action not sitting on bench taking selfies and talk some random batter.

Most relationships will fail because of trivial boredom, it's a all big show but people don't want work and entertain each other, they are too used to instant dopamine boost provided by media. Men have dopamine addiction from porn, political news and computer games, women from social media. No human can compete with never ending stream of dopamine.