Finished it, great game but overall I think both Galxies and 64 are better.
My biggest gripe with Odyssey is that it took the worst aspect of BOTW and applied it to the whole game; ie the collectible power moons being everywhere with no real challenge or reward from collecting them. The game favors you doing countless little tasks such as simply talking to someone, a ground pound, collecting musical notes, etc - versus the more challenging platforming segments you needed to do in previous games to get a star. Not that this is a totally bad thing, as the constant collectibles make the game seem fast and always gives you something to do. I just wish they were utilized better. The (mostly) linear path of the rather few worlds was disappointing, I would have preferred a more traditional "collect x moons to unlock this world" vs collect x moons to leave and go to the next. Purple coins can be as challenging to get as moons sometimes but the rewards are purely cosmetic, which gives me little incentive to go out of my way to collect them. They should have been used to unlock sub areas in worlds or something.
Beyond that, there is almost zero difficulty curve in the game. Some of the later worlds weren't any more difficult than the early ones. The final bowser fight was only slightly harder than the first. The cool Bowser segment at the end slightly made up for it, but almost felt undeserved. There also was a strange lack of standard Mario worlds like a Boo/Haunted world, which I felt could have easily been done in the awesome Ruined Kingdom which wasn't utilized at all despite having great aesthetics.
The mechanics of the game are excellent however and probably the best of the series in that respect. Capturing enemies was the highlight of the game, and they mostly utilized it well. I would have liked to see more than one or two captures per area to unlock more complex platforming ideas but I can't complain too much. The 2D segments were fantastic, I think they could have been more creative though and brought some of the 3D features in 2D, like capturing a bullet bill in 2D would have been awesome.
-No, you didn't "finish" the game if you haven't touched the post-game stuff
-None of these pointless tasks (ie. talking to someone) is required, so it feels cheap to criticize them. There's simply there for those who want an excuse to spend even more time with the game. There are more than enough power moons that require skill and platforming
-Your point about difficulty is also completely moot if you haven't done post-game. There's literally hours and hours of new challenges that are actually difficult. I've died hundreds of times trying to complete some.
I think this game utterly destroys Mario 64 and Galaxy, even though those games were masterpieces in their own right. But Odyssey has a level of content, polish, variety, and nostalgic love that is simply on another level.