What went so wrong? I remember the times when this was praised to the heavens and now nobody talks about it anymore

I agree. If you are interested in something that does this right. Look into Angolmois

The author isn't a woman.

People were praising Vinland back in 2015 because that's when Farmland wrapped up and people (including myself) really enjoyed it. It was a nice ending to a long but well-done arc for Thorfinn.
However since then the manga has had a shift in tone to a more "happy-go-lucky" one with more slapstick comedy, more and more characters with shallow backstories were introduced (forcing other great characters like Einar and Canute into the background), and overall the pacing's been kind of all over the place. Then the anime came but nobody on here cared much due to shitposting or people kept complaining about what's happened in the manga, making discussion about the anime virtually impossible.
The reason why the manga's gotten worse is because the author Yukimura quite visibly got tired of writing sad/depressing stuff over time. He's commented how he's a father of 3 now and he wants to enjoy himself by writing/drawing a more "happy happy joy" manga with a simple hero who now has a family and faces silly villains. Like, he literally did a timeskip and COMPLETELY SKIPPED a potentially interesting arc that was vital to Thorfinn's journey in history and that had LOTS of buildup, to instead rush into a final arc and introduce a transgender viking.

He's been a father since the first volume so what you're saying makes no sense.

I don't understand why people are caught up on the pacifist thing. he is not even a pacifist. he fought the spear dude he just doesn't want to kill people. thats not the same thing as pacifism

I think the point is that a pacifist character in brutal medieval viking times would stand out but Thorfinn always comes off as such a hypocrite.

The story built up some fantastic character development for Thorfinn as he went from a revenge driven viking to a literal slave who spent years finally learning to move forward. Then it decided to smoulder and burn.

Then the Baltic Sea arc happened and with it came a few problems. Hilde as an external representation of Thorfinn's bloody past could be fine but she's far too blunt a character and not interesting either. The spear autist fills a similar role, reflecting Thorfinn's edginess without the same backstory to justify or contextualize it. He's the shallow representation of what Thorfinn was. The sheer amount of time dealing with Floki and his bullshit just ate away at the story. And Gurdrid and the baby are equally annoying for how they impacted the story.

The story also started to suck off modern ideologies more often although I still think some moments like the viking dying and musing about the afterlife after the raid on Floki's compound was good. But that snowballed into a transexual son of Thorkell. We also skipped Istanbul (no not Constantinople) so fuck merchant saga I guess? We need more politicking.

Baltic Sea was already a slog, a true slog not what people think of Farmland Saga. And Thorfinn's character is no longer interesting when his ideology can only confront caricatures and cardboard cutouts. It's shit now. It's like how Berserk took an arrow to the knee in terms of quality after Guts got his new crew.

Based Yukimura triggering retards

While I agree, this was evident from the very start, or after the longboat carrying

This is some buddhist thing about going from one extreme to the other and finally finding balance. But who knows if Thorfinn finds balance in Vinland the story moves so slow. Also Hox left because he was pissed about Grikkland.