Would you rather have Adventure 3 or Unleashed 2 or Sonic and the Black Knight in Space, or would you rather have Rush 3, Retro style?
I thought so.
That's exactly what bugs me about this game. It tries to be like the classics but fails in the biggest respect: It's "Retro-style" gameplay comes off as a sloppy approximation of the real deal. The homing attack negates any real challenge, the gimmicks aren't used creatively in combination with each other but are instead limited to specific acts, any momentum-based physics are rendered useless by Sonic's ability to run up walls, and in general the game feels excessively fast and loose (compare the advancing-wall part of Lost Labyrinth 3 with that of Hydrocity 2. One is a slow, suspenseful escape and the other feels like guesswork, mostly).
One can't really blame DIMPs. They've been gradually shoehorned into producing their signature "slick-as-snot" levels. That's what they know how to do, and when they do it well I think the experience is rewarding. But trying to mix it with the slower-paced Sonic gameplay looks awkward, to say the least. I guess I just basically hoped they wouldn't pursue both classic and modern gameplay elements if the result was going to be as half-assed as it is suggested in these videos.
And speaking of half-assery, the game smacks of a distinct lack of effort in many aspects. The most blatantly obvious example is Casino Street 2, which I think is really cool in concept (if you don't know, the player must gather 100,000 points on a pinball table to pass the act), if the playing field were expansive instead of obnoxiously small with only one real way to gather the necessary points (flip into the point dispenser at top. Maybe fall into slot machine. Rinse. Lather. Repeat.) But then there's also pathetic collision detection, most obvious whenever Sonic is situated on a pinball flipper, as well as what I think is the terrible creative crime of not being willing to mix gimmicks, instead limiting them to distinct acts. These sorts of problems are rarely cited in the classic games. Small things like this matter, dammit.
All the above plus the music is why I'm not excited about this game at the moment, in a rather large nutshell.