I think the scene in the sept was a good idea, but found it frustrating that Rhaenyra stops short of explaining the entire prophecy to Alicent. It's like once she hears the information she's looking for to answer her own question she doesn't take it any further. If you're trying to negotiate your way out of a war after there have been injustices and murders on both sides, you'd better have a damned good reason. A prophecy that could doom everyone IS such a reason. But instead she brushes it off as "it was this story my father used to tell," like NO dumbass, it's existential and the entire reason he named you his heir! To call that a missed opportunity is an understatement. It seems so pointless that they had that conversation only to resolve to go to war anyway. Rhaenyra, if she REALLY cared about the prophecy, could simply offer to step down from her claim and meet with the council at King's Landing to explain the prophecy to them and collaborate on a plan going forward. But I think she wants to be queen for the sake of being queen, like to validate her father's love for her. And Alicent obviously doesn't care that both her sons are rabid psychopaths, so she's an even worse problem.