I've been having a good amount of fun with it!! I knew that it wasn't The Worst Game In The World and that its notoriety came from being such a big, confident release that was so clearly unfinished and rushed. And I also knew I was going to have some fun with it, especially with all the jank, but surprisingly, the unfinishedness of 2006 is not such a big slice of the fun!

It's honestly a pretty alright game all things considered, especially compared to Heroes or Shadow the Hedgehog, which are think are definitely less fun. It's clearly trying to iterate and put its best foot forward on a lot of ideas that were being played with by prior entries of the franchise, like trying to figure out how to create more depth with the combat, for instance.
I couldn't forgive it back then for its misguided tone and visual direction, but now I see it as growing pains of an early title of that generation. They were trying to figure out, as many other developers were, how would their game look in the new hardware, how to set it apart. Some games went with the horrid brown filters and lots of bloom, and Sonic went with a visual direction that unfortunately furthered the uncanny disparities of these cartoon animals next to things that were not... as cartoony. And obviously, they didn't have the time to get further acquainted with the new technology and figure out a better art direction. But now that we're far away from Sonic 2006 and I don't have to worry that Sonic is heading towards a direction that seemed to disregard everything that I loved about Sonic games, and can see it from a wider lens, I have more sympathy towards what the developers were trying to do.
If the game didn't look like it did, it's possible I wouldn't have had an issue with its tone and story at the time... It's possible I even would've had no issues with Princess Elise, even! I see what the dynamic they're going for is, which is kinda what Amy was in Sonic CD, they want a character that isn't a hero to be cared for and inspired by Sonic's heroism and character. A character that doesn't feel like they can do all the things that Sonic can do, who wishes had Sonic's carefreeness and strength, that loves Sonic for all that they feel they can't be. And then Sonic moves on, because he can't stay around, and Sonic going away helps them understand that they can embody these traits themself, and rely on their own strength as they move forward with their life.

But Sonic Team was, at the bare minimum, very misguided into not addressing the uncanniness inherent with Elise and Sonic together, in believing that Elise would instantly communicate that appeal, that the relationship between the two would be obvious and accepted quickly. And then not stopping at the adoration and letting her kiss him, while Amy's right there, unreciprocated, and donning all the appeal, acceptance and history to the character, while Elise has none of it, and worse, the uncanniness makes people have this image that she's a grown woman kissing something between a child and a pet animal.
But imagine this, imagine if Elise was highly stylized and looked cute and appealing next to Sonic, and looked younger, rather than an adult. Even if she was still a human and not an animal person (though the latter would certainly help). Imagine if she didn't get to kiss him and was just a crush that Sonic accepted but didn't reciprocate, like how a school teacher treats a student's crush - something they'll grow out of, but hoping to instill something positive in them, to be a good role model for them, until then. I think that's probably the kind of feeling the developers wanted people to have with Elise, and I think that would've worked okay.

And when it comes to the game itself… The stages are long but I don't feel as tired as I do with Sonic Heroes, for instance. The levels have a good amount of variety of things to do in them, and go through many different beats, which helps them feel not so tiringly long as in Heroes, for instance.
But ofc, stuff doesn't always work like the level design intends it to, which leads to some minor frustrations, but that's the keypoint here: All the frustrations I've felt with the game so far are weirdly minor, & I think this is why it's such a popular game to stream, it's like Baby's First Kusoge: It has the appeal of a Kusoge or a Bakage (weird shit and behaviors happening, getting killed for comical reasons) but without the enormous frustrations that comes with a lot of Kusoge - Sonic 2006 isn't a hard game or a very punishing one. Lose all your lives? You just re-do the level you were on. You don't even lose lives in the hub world! And most of the times you die that are "not your fault" are funny and fun, especially if you're passing the controller with a friend, or are doing it on stream.
All the ways in which it is clearly unfinished are amusing and obvious, without feeling like torture. For someone who hasn't ever played a Sonic game, esp in 3D, it could be that it's way more frustrating, as they're still figuring out a lot of the language and inherent troubles with the "genre" of "3D Sonic", which it is a pretty unique kind of game that doesn't quite exist outside of the franchise, so it could be that part of its huge Bad Game legacy comes from the pains of people who are still figuring out "how to play a Sonic game" exponentially compounded with fighting the jank of 2006.
Once you understand that, you also understand why there are so many Sonic fans who "defend 2006", who say it would've been "a great game" if it was properly polished. I looked down on people who said that, but now having played it, I completely understand where fans like that are coming from - There have been several levels that I hadn't really died or ran into big issues with, because I've played Sonic games a lot before. But if I didn't instinctively know what the level wanted out of me in split-second decisions, it's possible I would've eaten dirt and ran into huge jank while I was at it. A lot of Sonic fans probably have a much smoother experience playing the game and can see the intent of the game more clearly. And, you know, a fan did make an excellent argument as to "how good" Sonic 2006 could've been with more polish: An argentinian dev known as ChaosX remade a lot of the game in Unity, adding a bunch of new features, fixes and improvements, and it's a really fun game as a result!

Honestly, what really, truly brings Sonic 2006 down besides the obvious fact that it's a rushed and unfinished game, why people don't feel comfortable calling it an "Adventure 3", is that 2006 lacks the qualities that truly elevate the first two Adventure games. After all, it's not like those games don't have their shares of jank and misguided decisions, even if there's less of it than here. What elevates SA1 and 2 is that they have big, cool moments with characters people love, they have Live and Learn and Open Your Heart, they have an attitude and energy to them that's so captivating. Sonic 2006 doesn't quite have that, as much as it's trying to make you remember the Adventure games as you play it.
SA1 establishes all the characters' personalities, it has Tails learning to be self-reliant, Knuckles learning his past, the entire plot with Gamma, SA2 has Sonic saying his final words to Tails and Amy, it has Rouge and her dynamic with Knuckles and Shadow, it has allll the Shadow stuff, and Sonic's rivalry with him. Sonic 2006 has a lot of returning characters, but they don't get to do much, or have big moments that develop them further. All that it has are the new characters, so it really is a game for if you're a big fan of Elise, Silver or Mephiles, I guess.
Sonic 2006 is just a bit too sterile, and doesn't capture that energy that makes Adventure 1 and 2 so well-liked. It's a game that can be funny on purpose, but that's mostly on the wacky NPCs. Oh yeah, did I tell you about Soleanna? It's a pretty fun hub world, and through its people and missions, they really want to impart the feel that Soleanna is a character all of its own, with its history and culture, and throughout the game, I did get a little bit endeared and cozy by it, which is exactly what a hub world should be like. At least the New and Old cities, the Forest area is just very barren and without purpose.