Haven't looped around to play Mario 64, but I don't think it Odyssey should be considered a Mario 64 level classic. Actually rounding up all the collectibles gets annoying. (Like the time they put regional coins just under exactly one cliff of the extremely wide Sand Kingdom.) It's my understanding that part of the reason people like Mario 64 is that it's relatively compact.
If we're looking at it as a classic of the Switch 1 generation, then I'd say it definitely is but in a more broader scope, I'm a little less sure. It definitely has its flaws and I personally have no desire to replay it like I do with the Galaxy games but I still think there's an argument to be made in favor of it being called a classic because of how beloved it is in general.
Odyssey is in some ways - enemy types, the Capture system - a breath of fresh air, but in others, I find it disappointing. Primarily level design. Its open nature results in it lacking the same tightness of level design previous 3D Mario titles had, and its maps feel so filled with empty, pointless space.
It's far from a bad game, but I wouldn't personally call it a classic.