Thank you all so much for your positive responses, I was not expecting so many people to feel similarly! I am most pleasantly surprised!

Originally Posted by Tarlonniel

Wood elves get a special interaction with Kagha. I don't remember them getting unique lines anywhere else, though (aside from the few generic elven ones).

I know, that's why I said I was expecting to be able to deity-shame her, lol! The special wood elf line combined with all of the elven NPCs around the druid grove make it seem as though it is standart for a wood elf to worship Silvanus.
And while some wood elves do, the Seldarine are literally their ancestors, so it makes so much more sense to go with Rillifane. Anyways, I get that not every deity gets to be included in the game, there are so many! But all the details add up.