Gay man here. In a long term relationship. Also have lots of straight friends, so I've heard about that side of things as well. I think the trope of a happy marriage requiring sex is just as harmful.

The truth is that a marriage needs as much sex as it needs, no more, no less. There are people who are perfectly happy in sexless marriages, and people who are miserable in marriages where sex isn't a problem.

The most important ingredients for a happy marriage are two people who are well sorted ou. Everything else is negotiable.