The back story is that Nemesis was commissioned before Remembrance. If one had been cancelled due to plot similarities, then Rem would probably have gone. Thankfully not."Silver Nemesis" was mediocre. It always bugged me that it was treated as the official 25th-anniversary story instead of "Remembrance of the Daleks," which was not only a far better story but a more logical anniversary story. "Nemesis" seemed redundant, an afterthought and an anticlimax.
30 years ago I wondered why the anniversary story had been assigned to someone who had seen very little Who, and had presumably made a point of avoiding it given his age.