Short version: You're dead inside.
Long version: LOL, not really. It's a different kind of Mario game from his recent adventures, and even a step away from SM64's sandbox approach. It doesn't have as many traditional obstacle-course-style objectives, which many players enjoy. A lot of Mario levels feel like clockwork contraptions that only really work when you slot in the missing cog: Mario. He makes everything tick as it should. These worlds are purpose-built for him. Meanwhile, games like Odyssey and Sunshine, to an extent, feel like places that could exist without him. Each approach has its pros and cons. Part of the reason people like Galaxy and its sequel so much is that they find a nice balance between the two styles.
To address the criticism of the so-called 'throwaway' moons: they're there to give less experienced players a way to reach the finish, to reward explorers and give younger audiences a sense of playful discovery. It is, however, a game that at some point is going to annoy anyone who just has to get 100% completion, simply because there are tasks that weren't necessarily designed with that type of player in mind. Some are going to really struggle with a few of the more challenging late-game objectives. By the same token, those who enjoy testing their twitch platforming skills are inevitably going to be a little disappointed with the moons you can get your hands on with little to no effort. Here's the thing: you're not really meant to get everything. The option's there, but at the same time once you've seen the final kingdom – and let's face it, the barrier of entry isn't that high; there are tons of moons still to get if you head there at your first opportunity – there's nothing stopping you from quitting. That's why the very final rewards for the most dedicated players aren't all that exciting: the game doesn't want to withhold anything really desirable from the majority of players who don't necessarily have that desire to wring it dry.
You could argue that having so many moons diminishes the sense of achievement, and maybe there's a kernel of truth in that. Then again, Nintendo has always made games where the reward is not the shiny trinket at the end, but the sense of accomplishment that comes with it. When you conquered Luigi's Purple Coins (or whatever) you weren't happy because you got the star, but because you'd beaten a difficult challenge. So I don't really buy the criticism that the moons don't mean anything.
For me, a lot of the joy in Super Mario Odyssey comes from simply moving Mario around. He's just a pleasure to control: amazingly responsive, with a wonderful, flexible moveset that lets you pull off all sorts of neat little tricks. And the balloon bonus mode - which itself seems like a throwaway addition - lets you use it to its fullest, because you'll need to be clever to get some of the most well-hidden ones (and to find yourself a good spot to place your own). I'm one of those players who did wring it dry, who got 999 moons, who saw everything there is to see. And I still find myself going back every now and again – sure, partly to farm enough coins from the Bowser Kingdom beanstalk challenge to buy the new costumes they keep adding, but mostly because I just love the feel of the thing. I stick it on, run and jump and throw my cap around a bit, maybe hide or find the odd balloon, and that's enough for me. At the same time I don't blame anyone for wanting something more, or something different. It's just a matter of personal taste.
