It is bar none my least favorite game of the franchise. Especially in relation to the other Switch games, it's at the bottom of the list, even below New Snap.
While it's a cool idea and has some neat mechanics and concepts, it just doesn't work for me. Personally, Sword is my favorite of the Switch games, followed by Scarlet (Sword is actually just one of my all time favorites in general, but that's a whole other discussion) and I feel like Arceus is such a letdown when compared and I never understood the overwhelming warm reception it got as a result. While it's neat in theory, the whole being thrown back in time concept just isn't interesting, and while I did enjoy fighting the Alphas on each subsequent area of the map, overall the plot just didn't keep me invested. And that would be forgiveable if it weren't for the real damning issue in regards to the game, which is that it's essentially Pokemon Go but with NPCs giving you fetch quests. Filling out the Pokedex has always been a thing, I'm not even going to pretend that it wasn't. But in those instances, you were doing it for yourself. Because you wanted to. Now, in order to fill out this Pokedex, I need to catch 18 different Magikarp for an 8 year old so she understands the concept of a fish (alright, I'm being a little hyperbolic but you get the idea). It's tedium turned to 11. And I say this as someone who doesn't even mind repetition or anything, but my lord, there's a limit.
The sad thing is, the game, as I said, does have some great ideas. The overall Alpha clearing, the semi open world is very well done even if its somehow emptier and less interesting than Scarlet's (and I say this as someone who hates open world games) and crafting, for once, isn't a detriment but actually works. Usually when a crafting mechanic gets introduced into a franchise that it's not only not necessary to have but also never been used in before, it's a sign of simply buying into a trend. But somehow I don't mind it here. It's perfectly fine, and honestly, it makes sense given the timeframe that the takes place in. You'd kind of HAVE to craft things in order to succeed at that point in time because, while there are vendors around, there's no real shops exactly as there are in the modern day games. Crafting potions and different kinds of balls is very cool, and that's something that did surprise me given my aversion to unnecessary crafting mechanics. So there's stuff to like here, but what it's wrapped up in is so bland, dull and uninteresting that it brings the whole package down. I also didn't mind the fetch quests for finding stuff other people had lost. I thought that was kind of fun, because it was something you could chose to do or not, it wasn't like the Pokedex, which literally locks you out of progression if you don't do it.
For as much as I've never understood the love for this game, I've also never understood the hate for Scarlet and Sword and the other newer titles. Sword is perhaps the single most polished and perfect Pokemon game to date. My favorites are Silver, Black, Moon, X and Sword, and Sword beats them all just because it's such a perfect combination of everything that came before it. Arceus isn't a combination of anything other than half baked ideas from better made games, and even then they're doing poorly even by Pokemon's standards. While I do recognize Scarlet might've had some technical issues at launch, I personally have never run into them myself, and the game played fine for me, albeit some occasional lag here and there. Frankly, between Scarlet and Arceus, I much prefer the open world of Scarlet, simply because it has a real story tied to it and the world feels alive. The world of Arceus, sans the Pokemon who live in it, doesn't feel alive in the slightest.
I got Arceus as a gift, and even without paying for it I was still disappointed lol