Aren’t some of the Desolate Council still alive? In Before the Storm some were rejected by their living relatives (and Sylvanas exploited that, saying almost word for word “no one loves you like your Dark Lady does”), others tried to defect to the Alliance and were killed for it (which is fair, that was treason) and those who were killed for re-connecting with their living relatives. Didn’t Zelling have living relatives he was in touch with? 
Hasn’t Sylvanas been a major character since Warcraft 3: Frozen Throne? She got as much spotlight as Arthas in the undead campaign. Then from Vanilla to Wrath didn’t we get to know Sylvanas? I think I have that “Lament of the Highborne” toy on my characters. 
I’m not sure what they could do with Genn. He and his people also lost their homes and lots of loved ones.
I think the lack of empathy for Sylvanas fans might be due to people being more focused on the Night Elf fans since the Night Elves didn’t even get one cinematic despite being the victims of the Burning of Teldrassil.
The potential of being used for a “religion bad” message is only one of the problems I had with the villain-batting of Yrel and her group. It is poorly written, out of character, whitewashes a war criminal and ignores a big swathe of the lore. I’m surprised you say you agree with me about this leaning into an atheist agenda (a concern but not my only one) given some of the things you said to - and about - me on a thread about that very topic, such as;
What changed?