It was better than most other attempts at a visceral Viking movie, but hugely underwhelming for me overall. There were a lot of mistakes (his mother's unchanging age between boy and 48 year-old actor is just one of many).
And it all felt rather disjointed, like Eggers couldn't decide whether he wanted a rambunctious action movie or a metaphysical arthouse flick. Sometimes those allusions can work well together, here they clashed, making the movie tonally inconsistent.
I didn't hate it, but it is very flawed. I thought The Green Knight was a much better film. It knew what it was going for — a slower-paced bit of mid-budget arthouse — and hit every note with precision and deftness.
As someone else posted above I actually found it hard to watch in one sitting. The thing that pulled me through was Taylor-Joy's amazing face, but that's honestly no reason to recommend it.
The Northman's not half as clever as it thinks it is, and given too much credit for a philosophical texture largely projected onto it by its audience, when in reality it's terrified the world will see right through it to the vapidness at its core. It's the Jordan Peterson of mud and blood epics.
Movie is a 6/10 for me.