there was rarely if ever any real consensus what was wrong with Sonic or how to fix him. But Sega never really stopped trying, either.
It's what bugs me the MOST about X7.
The potential was there, the game looked good, the underlying concept of X in 3D was there and worked more or less, it just needed fine tuning. They needed to take what worked in X7, and play with it.
Command Mission came out right after, and while it was a completely different gameplay style, it still seemed to improve on some of X7. Cutscenes were all cinematic for the first time since X4, using in game models, the 3D world felt immersive, the areas unique and well thought out, and nice to look at, and the actual gameplay was fun. And overall the game felt like the dev team really enjoyed making it. The amount of detail and thought that went into it tells me as much. Of course you can barely compare it to any other X game, but still.
Then X8 comes out and it's just a 2.5D X game with bland forgettable level design, terrible gameplay choices, (putting every single item into the shop therefore killing much of the stage replay value). Graphically, I still say X7 looks better than it- a lot of the music just felt too samey to me, and only some of the OST stands out IMO. And overall, X8 just doesnt feel like it has anywhere as much soul as the previous games. It just feels too alien compared to previous 2D entries. Even X7's 2D sections felt more traditional X series than X8.
Aaaaaand.... we never got another X game past X8.
It bugs me they never tried to fix the 3D formula for another try. It's what the franchise really needed.