Read the thread, you'll find several posts discussing the subject at length. I presume you're anime-only, and anime adapted two arcs that pre-date the brainrot of the author (prologue is shonen-lite and Farmland Saga is about THE EVILS OF SLAVERY AND GOVERNMENT, but it's still decent).
Vinland proceeds to introduce random female characters that are perfect because they're female, viking Japanese deliquents, viking trannies and after a lot of confusing useless chapters they go to America where the plot tortures itself to preach absolute pacifism and how the Injuns are magical and did nothing wrong as they're slaughtering you but it's inhumane to resist. The author himself on post-scripts preaches how he's so horrified by the brutal, savage vikings and how they're a terrible culture and how Strong and Brave should have been their women or something.
He also time-skipped Constantinople and that's the last straw, the last fucking straw.