The basic premise of all art--even porn--is that there must be a narrative. The human brain is geared towards narratives, probably out of a need for survival (or fun or both). So any romance is going to have a mystery problem or a historical problem or a contemporary problem (someone is dying, someone is trying to save a town, someone is trying to reconcile with one's family, someone is dealing with a legal tangle).
Some of these romances are what I call trope romances, a collection of classic tropes and erotic scenes squished into a narrative thread. And the big give-away for pure trope romances is the ending.
In these types of romances, once the revelation occurs ("I love you. You love me.")--the story is over! That's it! No more!
I've read romances where the writers/narrators basically ended with the following throw away lines (I'm making up the words but not the endings):
"Oh, and then a few months later, we caught the murderer."Okay, I made up the last one--but you catch my drift.
"And then we found a cure next year after we were happily settled."
"And then our families started to get along."
"And then the dam was repaired and the town was saved and the asteroid was diverted and by the way, Superman flew around the world backwards."
When I assign narratives in my business and academic writing courses, I instruct my students that they may tell a story about themselves but they cannot end the essay by talking about themselves. They have to use the narrative to prove a thesis. And the conclusion of the essay has to be relevant to the READER, not to the self-absorbed, navel-gazing writer.
Fiction writing is not the same as essay writing, but the principle holds true:
If it's a murder, solve the murder. If it's a war, wrap it up. If it's a terrible disease, find a cure or kill everyone off--either is fine but DO IT (i.e. SHOW IT)!
But ending the narrative when the couple declares its affection is frankly, obviously manipulative. It says, "Oh, you, the reader, are only reading this for the love scenes. You're such a dopey romance reader. You don't care about good stories. You only want your HEA. As long as I give it to you, you won't complain."
I do like HEAs. I am a dopey romance reader. And I will complain if the story arc stinks.