Maria Baez is Danny Reagan’s best bet for a series-ending romance in Blue Bloods, even though he doesn’t deserve her. Although Danny is one of Blue Bloods‘ best characters, he often caused unnecessary problems in his marriage to Linda during the first seven years of the show because of his hotheadness, stubbornness, and overprotectiveness. Linda died off-screen between seasons 7 and 8, and Danny has been grieving the loss ever since, though in season 14 he decided he was ready to date again after realizing he was holding back out of fear of suffering another devastating loss.
https://screenrant.com/blue-bloods-danny-baez-romance-ending-reason/