So the "steps" would be like the "talking" phase, the "hanging out" phase, the "situationship" phase, the "friends with benefits" stage etc. All of that could take years before they decide to move in together, the couple might have a few kids together, before marriage is even talked about. I know people have different takes on marriage and family, but it just seems silly to waste so much time on someone who fundamentally doesn't want what you want. When on the flip side, you could know a person for two weeks, gone on three dates with them, and they're the person there willingly and happily taking care of you when you're sick, helping you babysit your nieces and nephews, and planning your grandpa's funeral, etc without demanding anything from you s*xually. If you're life goals are the same, why not be together? - hence the whirlwind romance.
In storytelling, it goes back to what I was saying about being smart/local about it. A lot of romcom couples won't work out in the long run because their relationship was just a game. I opted not to do a will they/won't they couple in my work because the relationship becomes a source for drama which in real life usually equals toxicity. If they like each other, work well together, and face problems together as a unit - why not put them together? One of my favorite male leads, his way of professing his sincere love for his partner was by being there for her - she went through chemotherapy - he was there holding her hand. She wanted to settle down and become a mom, he volunteered to be her kids' dad and support her every step of the way. To me, those couples will never be corny.