Thats just your opinion on that matter.
I don't see the issue here. Everyone can change if they want to.
The Greek Storyline was about how the Olymp screwed him, which led to his family being killed and Kratos revenge on those Gods.
The new storyline was his 2nd chance with a family and his fight against his old self to prevent similar things happening to his new family. Thats why he needed and _wanted_ to change.
3 years had passed since then. He had plenty of time to speak with Mimir about the prophecy he saw about his own death. Plenty of time for change in personality to happen.
In the original games, Kratos was almost a cartoon character and his actions were way past redemption. He was a dark god and there is no forgiveness for his actions.
In the 2018 game, they had to face that. So they put the story hundreds of years into the future, where Kratos was in a different place and in a different situation. There are almost no explanations for what happened, and we don't know how or why he changed apart from meeting a woman and getting a child. This was a great move from Barlog, we didn't need to know, and there is no need to detail all of it, we can draw some loose conclusions that were enough to accept the new story.
But, he is still Kratos, and the way they dealt with that is by having him be harsh to his kid, and be silent on what he had done in the past and stuff like that. There was a vibe and mood to him that made us remember his past but understand his new ways. This way, they could maintain the character and make him a bit more realistic. It was a tightrope, and they pulled it off.
In this game however they go a lot further, they make him reason more and behave and act like something that does not match his original games. There is a disconnect. He cares and acts more like a human. They want to have a character with traditional story arcs and character developments, completely ignoring that he is at heart, a dark god.
What follows, is absurdity like Kratos cracking jokes and following other characters around, trying to get them to like him and be his friend. He is never the real Kratos in Ragnarok.
I don't think this is the greatest of the games' story sins, the exposition about places and characters that are not developed I think is far worse. For example, how characters force us to listen to history about places we have no association with, the writers are so desperate to "develop and build" the story about each place, that they have companions constantly blabber about what has happened and what each place is for, to the point where the game never shuts up and every companion has voice lines that are completely unnatural and so predictable you can set your clock to it. Every 20 seconds they go off. It's a tired and overused video game story trope.
