Maybe in the past. We're seeing the opposite of that a lot more lately. That the concept of entering into a relationship isn't the end of the story. That it doesn't magically solve all problems. That acting as if entering into a relationship isn't a trophy or prize or reward.
Too many people use Moonlighting as their example of the relationship killing that series. We are also about thirty years removed from when that series was on the air.
Some of Brooklyn Nine Nine's best episodes happened after Jake Peralta and Amy Santiago got together at the end of season 2. And the internet was outraged when Fox canceled the show with season 5 before another network picked it up.