Where to begin…
Let's start with the gameplay. The gameplay loop is identical to the base game and its DLCs. Go there, find that person, do a thing for them, move on and repeat. Exploring also stays the same with a small twist, which is the Hugr-Rip, which you need to access some places and solve a few (very, very basic) puzzles. I was disappointed how the new powers were used. In places, it felt really forced and clunky. In combat, I had to force myself to use them, just to try them, even though there was completely no need. My character was already so strong from the base game and previous DLCs that any of the combat powerups didn't make the slightest difference. The only use I didn't mind was the Raven transformation, which was used to access Muspel Monoliths. When it comes to puzzles, they were very, very basic, and I feel sad when I think that we had puzzles like Subject 16 glyphs which were fairly difficult and even gave us more info on modern day Assassin/Templar lore, and also gave us hints about the ISU. If you needed to use a powerup during a puzzle, it was always the Jotun teleport or Muspel magma walking. If you didn't have one of those powers already saved, you had to find a body laying around which had the power on it, but I felt like this broke the flow, because I had to go out of my way, even though I knew the solution to the puzzle (not that there would be any rewarding feeling finishing the puzzle).
The visuals felt alright, about what I would expect from AC by now, I especially liked the design of Eitri, since it felt very different to what we've seen (maybe excluding Tartaros from the Atlantis DLC). Though I did feel like 3/4 of the map were pretty much identical. Similiar to how most of base game's map felt very, very similiar (yes, I know, it's Britain, trees, rain, lots of grass). But since this was a DLC, I expected maybe something… more. Just look at Fate of Atlantis, or the Asgard map from the base game.
Now, the story. This was the biggest lettdown for me. The story basically didn't tell us anything, until the very end. The "mythological" story was very vague, not much happened until the very end. Now, when we look past mythology and focus what it was meant to represent about the ISU… Still not much. There was Juno, who at the end had access to the Salakar, possibly somehow using it or its technology in the Grand Temple for her Aurora Borealis project (we saw one tower of the project at the very end), maybe that's how she was trapped by Minerva and Jupiter inside the temple. Other than that, we still don't know anything new. With one possible hint that Baldr will somehow come back after Juno sets the souls/consciousnesses from the Salakar free. We don't know anything tangible, only Eivor's interpretation of the events, which is heavily influenced by the mythology she knows. The story could at least have a pay-off at the end, if we got to play through Ragnarok as one long final sequence, but that didn't happen either, which makes me thing there will be a chapter 2 to the DLC. Odin at the end hinted that the battle will happen soon. There are also dams on the map, which contain some sort of portals/gates which drain any intruders of their life, these weren't used in the game at all.
Finally, the price. 40 €. Seriously?? On top of season pass? This DLC took me 20 hours, 5 hours give or take. at least 2/3 of it were mindless exploring on autopilot, just like the base game. No challenge, nothing interesting for most of the time. The rest was the main story. I completed 100 % all the regions, except for Kara's stories/challenges, which I was already fed up with after the Valkyrie challenges in the base game. It's just a cheap way how to prolong game time, 20 (or something) challenges which are all just combat with restrictions. It's boring. No one wants to play through that, Ubisoft. Maybe if the combat was more complex, or refined, or more challenging, with a much better pay-off, because I really don't want runes, armor or weapons, I already got plenty from my 159+ hours from the base game and DLCs. The price was just too much for what we got. And even what we got wasn't that good.
I'm sorry. I've been playing AC on launch ever since AC:II, but I just feel sorry seeing how the series is in decline. Maybe more and more people still buy the game, but the series started losing its soul long ago. Now it's synonymous with a generic cashgrab series made for masses, so even the worst player on Earth could finish the game blindfolded and hands behind their back. You almost completely ditched the modern day story, killed off Desmond, and solely focus on the historical stories, even though the real plot was always modern day. I want modern day. The fans who care about the story as a whole want modern day. And I know you're making the Basim game set in Bagdad (I hope that's true at least) but this really should've come sooner. Please, expand on the ISU, expand on the Templars and Assassins in the modern day. Not just by making us read random letters and database entries, but with actual gameplay and cutscenes. I wouldn't have anything against a little fanservice down the line, like having Desmond return (and I guess also Layla) and making him the protagonist again. We know his consciousness is preserved, maybe Elijah (yes, Desmond's son, which feels like something important but was for some reason thrown into a comic not many people even know about) can somehow bring him back. He knows about how Juno was trying to grow a new body for herself, why not attempt the same for Desmond and Layla. Just give the fans a pay-off. Not just within the historical stories, but within the "real" story/plot. I'm sorry this turned into a ramble.
EDIT: literally hours later I found out there are actually multiple hidden puzzles and cyphers, so, joke's on me, I guess. I was very pleasantly surprised by the complexity and that such small details are present in the game, even if there are only a few of them. Thank you, people who work on these secret puzzles and the ISU language. Youtube took me down an interesting rabbithole, if anyone's interested, check out Access the Animus on Youtube.