The writing is not bad, and in all fairness I did get this during Stuff Your Kindle day but I do feel like stronger editing was needed to make this a good story. It's alright, but the comments below go over what should be improved to leave a more lasting impression.
Birdie's meant to be a neurotic people pleaser whose fake date for the holidays skips out within the first page. We don't see much of that reputed neuroticism outside of various characters mentioning it. She doesn't seem to feel any discomfort in denying her family, doesn't jumpy at every opportunity to make them happy.
Sebastian doesn't seem to have much personality beyond his puppy love and the various issues with his grandmother's dementia. It would have been nice if they really tried to explore the people they had grown into in the time they hadn't seen each other.
The age gap, although mentioned, doesn't actually play much into the story. Birdie's main challenge is a lack of desire to change anything about her living situation, so even though this desirable change comes along, she doesn't really want to jump in with both feet for it. That didn't make a lot of sense for me, since she wasn't moving out to a place with no safety net and no connections, but whatever.
The spice could do with some work, either in making it softer and more euphemistic to show a milestone of the relationship or going full ham and being explicit. I can't immerse myself in a scene where the MMC thrusts in at the beginning of the paragraph and the FMC comes by the mid-point of the same paragraph.
A few smaller things that bothered me were the author's difficulty with the conjugation of the verb thrust (which is still thrust in the past), and some very weird approach to the idea of wolf telepathy being something that they have to accept, as you would a phone call.