but with an emotionally mature partner, every other thing, including comfort and stability, naturally falls into place.

This is such a great point. You can love someone with all your heart, but if the other person is not emotionally mature, the relationship will not last no matter how hard you try and how much energy you put into it.

People tend to whisper or assume that one partner is using the other.

Exactly. And it's unknown whether they're actually using the other party or if the other person is totally ok with the arrangement.