Good things about Psychonauts:

• It's an extremely "robust" platformer for a game from 2005. There's a little Prince of Persia (acrobatic movement), a little Rayman 2 (minimal intertia in the core movement, a few number of buttons which allow most verbs (until you start unlocking bonus powers), and a steadily increasing collection of new powers) , and even a little Sonic Adventure/Sonic Heroes in there with some rail grinding and an eventual powerup with some robust pinball physics.
• The game is endlessly creative. It truly feels like something I have never seen before despite how old it is. I guess that's the "benefit" of the fact that it wasn't commercially successful?
• It's relatively non-janky for a platformer from the mid-2000's. Which means it's still janky, but given how much people complain about the jank, it's much better than I expected.
• The game tries very hard to contextualize everything you do in the game's moon-logic universe and it succeeds. So even though the game is chunked into individual levels, you reach each one by naturally navigating the game's overworld and progressing the game's story. There is such a sense of place to everything in the game, and the levels feel integrated in the story in a natural way that is unusual for a platformer.
• It's genuinely hilarious???????? I have laughed out loud from cutscenes multiple times in my playthrough.
• The game has the aesthetic of a Saturday morning cartoon series, but the humor is occasionally adult. It's not frequent raunchiness like a typical adult cartoon, just the occasional profanity here and there. It feels like a Saturday morning cartoon without censorship.
• There is a character named James Theodore Hoofburger who wears a cowboy hat

My major criticism:

• In most Nintendo platformers I have played, levels are an iteration on some gameplay idea. This game is an example of why Nintendo does that. By the midgame, you have a large number of items and abilities, so every time you reach a puzzle, you have multiple tools to approach any situation. There are some situations where a random ability you haven't used in 1 or 2 hours is suddenly relevant, and it causes what should be very simple puzzles to be frustrating flow killers. This is worst in the game's bosses, where I often reached points where I was completely confounded about what I was supposed to do (the solution was always very simple, which is the worst part). This doesn't mean I think the game should have the "one idea per level" design, but it could have done better to signpost to the player what abilities were relevant when.