Finished Mario Odyssey it was... ok. This game easily has the worst level design I've ever seen from a 3d Mario game and makes up for it by having an absurd 880 stars moons, most of which are just sitting around in the open or are attained with absolutely no challenge or even fun. The ones that do actually have some sort of platforming challenge attached to them have the level of complexity and difficulty of the beginner stars from 64, Sunshine, or the Galaxy games (I haven't played 3D World). The game never fully develops any concept it introduces. In Mario Galaxy a new powerup would be introduced and you would have an easy star to obtain with it, then a more difficult one that makes you use it in new ways, and then later you might get a challenge version of that same star that mixes it up again with additional challenge. Mario Odyssey gets as far as the introductory star, except in Galaxy a single star could take 5-15 minutes of unique content, where as in Odyssey most of the challenge rooms take 2 minutes tops. It's pathetic. The only real challenge comes from the final level where you have to complete a single level (like you might have seen near the end of previous games) in one go with no checkpoints, and it's not really hard, it's just time consuming because every time you fall down a bottomless pit you need to start way back at the beginning again. Joseph Anderson covers this lack of level design in fantastic detail and I agree with pretty much everything he says and highly recommend watching:
I don't think I hated the game as much as he did, I thought it was fine and even had fun during some parts of the game. I quite liked the New Donk City Festival sequence and liked the song enough to put it on my ipod, but a lot of the game was just there. Speaking of NDC why are there realistically proportioned people in it? Before playing I had thought that this game had some sort of dimension hopping theme, but it's not so, everybody lives in the same universe and even the same planet. The mishmashing of styles and bottom tier level design make it feel like this is a third party game wearing a Mario skin that's making use of an asset store.
There's also some odd audio choices in the game, like the areas that have absolutely no music whatsoever and thus feel very dull and the music before the flaming octopus fight that consists of someone halfheartedly hitting random notes every once in a while. Seriously, what is this?
This is the music playing in the lead up to a boss fight as you are running around unplugging geysers as he shoots boulders at you. How did this get in the game?
I think, like with Breath of the Wild, this is Nintendo's attempt to make Mario open world and it has a similar result. Quantity is pursued at the cost of polish and the experience feels watered down and bland compared to previous offerings. Honestly, as much as I was meh about BotW and it's lousy side quests and puzzles I actually think I might still like it more than I like Mario Odyssey. More and more I think Nintendo has lost their touch. Luigi's Mansion 2, BotW, Mario Odyssey have all been pretty sub par. Actually, looking through my list, I think the last game from them that I would consider unequivocally a knockout success would be Mario Galaxy (or 2 since it's just more of the same).
Again, like with BotW, I'm kind of floored by this because of how great everybody said this game was when it was released. People were stuff like it was the best Mario game ever made, and it made other AAA developers look like amateurs and stuff... and it is none of that. Anyway, I've done everything there is to do in the game except by some of the ludicrously priced costumes (why does every Nintendo game need cosmetic options now? I never had a problem with Mario dressing like Mario and Link dressing like Link.) I might play a little more of Luigi's Balloon world because it's actually kind of fun and then that's it.
Edit: I just remembered one last thing I wanted to say. Mario Odyssey feels like it is a descendant of Donkey Kong 64 rather than Mario 64. It feels like a collectathon and the way you need to make 3+ passes over every level to get a bunch trivially easy moons and search every nook and cranny for purple coins really reminds me of DK64, which is not a nice thing to be reminded of.