The problem with Luke and Noah were they were often very neutered and safe characters, as titan said above, with incredibly poor writing and stories at that juncture. The show prefabricated a couple they expected fans to go for sight unseen and didn't bother with truly good stories. They also had actors who, particularly in the case of Silbermann, often seemed like they really didn't want to be there. Any potentially spicy or exciting stories for them, like Luke's dalliance with Laurence Lau as his grandmother's new paramour, were ended quickly, just like any other potential good story on ATWT in its final years. The show was unwatchable to me.
If I wanted vanilla gays I'd have watched them. I didn't because the show sucked and the story sucked. OLTL's Daniel Colson story was a mess for different reasons detailed by several of us, but it wasn't because the story wasn't about saintly cardboard cutouts. Most of us around here have been eager for gay villains on soaps for decades.