Trek has never been good at believable romances, but Burnham/Tyler romance is honestly so far the worst, aside from the weird attempt at the end of TNG to get Worf and Troi to hook up. Plenty of "romances of the week" were worse however.
I think part of the issue is SMG's characterization as Burnham pretty much requires her to have difficulty expressing her emotions. But Latif is surprisingly unconvincing as well. This is a shame, because if they're taking the story in the direction I think they are (making him Voq, and hence developing conflict between his romantic feelings for Burnham and his hatred for her as the killer of T'Kumva) starting out with believable passion is a must.
I din't really feel the chemistry either. The scene in tylers quarters in episode 9 changed that though.