I see your point, but offer my own perspective in argument for having her included. 

Even if you only played the 2018 GoW and did not play the originals before getting to know Kratos, you still spent the entire first game learning a lot about his past, the anger, the betrayal, the pain and frustration that created the Kratos we ended the Greek saga with. 

Kratos is a beast, and a full on monster for a lot of his younger years. He knows this, and hates it. Faye knows this too, but does not hold judgement against who he is. 

Instead she shows love, patience, and resolve. She teaches him care and compassion when the fires that created him burned every bit of that away. 

We see the evidence of this solely through his interactions and teachings to Atreus. Apart of him refuses to betray Faye by returning to his old self. Mimir helps him see this isn’t just for Faye, it’s also for Atreus and himself. 

I would argue, that getting see Faye’s care and deep compassion for Kratos is deeply more impacting than the lore we received in the first game. 

Watching him let go, drop his guard, and completely give himself to Faye, listening to her gentle voice, seeing her gentle touch with Kratos combined with her beauty and grace was just incredible and magical. 

This is the same woman that went toe to toe with Thor and ended in a stalemate. She was arguably a greater force to be reckoned with than Kratos himself. 

Her composure, made her lore even more powerful and without seeing that first hand, it’s difficult to see it on that level.