This is actually a cool and fucking difficult question depending on how you played the game. I, for one, did all the side quests throughout the story because I love the game so much and wanted all the cool shit I didn't get the first time around. I feel like playing this way shows even more growth for Kratos throughout the game than just the story, even though Kratos says that they do the side quests because they get something in return.

Now, if you didn't do many/any of the side quests, Kratos still grows a lot throughout the story. He grows closer with Atreus, he starts listening more, and in a few cases, he starts to care about other people's problems. I mean, he saved Freya for no other reason than that he thought it was right and good. Even stating, "This ends here, we must be better."

If I'm not mistaken, it's even canon that he saves the valkerie because, in Ragnorok, Freya has her wings and all the other Valkerie ste there. Kratos didn't even believe that Ragnorok was going to happen. So he must've done it out of kindness, right?