That’s not Sargeras’s motives at all. Sargeras yes started out fearing demons until he met the dreadlords and found out about the Jailer and Death’s intentions, but along the way he decided that, with his grand view of the cosmic war, that reality is flawed due to it’s innate duality. That’s what Chronicle said and Medivh agreed with him and that’s why Medivh sided with him for a bit. Medivh ultimately realized that instead of destroying reality he needed to use a firm hand to help shape it.
Regardless Sargeras believed what he was doing was in the best interests of the universe if the universe was destroyed and remade to be better but better is subjective and in the eye of the beholder. A universe remade by the Jailer for example would NOT be a fair or just universe…
And that’s why I believe in Sylvanas and her endgame, and yes… her vindication. I believe she’s the firm hand Medivh wanted, the one the universe NEEDS. She’s the one who will “Master Death” and stop the jailer and through him she may have the power to form a more just cosmos.
I think it’s pretty clear that there are many who don’t share your analysis of Sylvanas being “selfish.” I’m not looking to start a debate on who she fundamentally is as a character, because if you know, you know. We shouldn’t have to keep defending our stance on this character, or why she has redeemable qualities simply because you and others fail to see or acknowledged those qualities.