I've defended the game on account the demo is suppose to showcase the gameplay, not the world or story. Thus these demos lack context on how and why Sonic is on such a small and bland island.
For all we know, this island could simply be the tutorial stage. Or may not even show up in the finished product.
Yes, some leaks showed that there's a desert stage too.
Hopefully there's a snowy one too or colorful one (like the one on Lost World).
Sonic Central is coming soon btw, may be there will be a footage of another stage.
I do agree the game still needs work and would allow (heck, encourage) Sega to consider post-poning the release of the game for polished and revised programming.
Sonic's general movement and boosting reminds me of Sonic Forces and we can't have that. Sonic Speed Simulator proves Sonic can work in an open-world game with Adventure-like gameplay and physics so Sonic Team doesn't really have an excuse at this point.
Yeah, if it's based on videos, Sonic Speed Simulator feels more fun to play.
Time will tell whether it's true or not.