I don't think it's becoming Sheldon centric. I do however, understand why some might be feeling this way. Perhaps if they allowed Lenny to have storylines separate of Sheldon more often, Lenny fans would stop feeling this way. I remember when me and my current boyfriend started dating my golden retriever would always smush herself in between us when we would start making out. Sheldon is kinda like my golden retriever. Anyway I honestly began watching the show for Jim so I wouldn't be interested in episodes where Sheldon wasn't an integral part of the A or B plot, but that being said Lenny or Leonard/Penny as their own sigularity should have scenes that don't focus on Sheldon.