Controls being sluggish and unavoidable movement restricting obstacles are not the same thing. They're both flaws as well.
A) the controls are not sluggish.
B) no. Are you aware of the definition of obstacles? Sonic's biggest obstacle would obviously be movement restricting ones, since he is mostly unstoppable when at full speed. Most of these are implemented probably so the game doesn't feel stale, many are also used to get you to unaccessible parts of the level and often reward you with power ups, so they are not entirely pointless. I keep bringing up Mario because it is basically the same premise, and you have to stop often and usually for more annoying shit in those games. One of the main goals of Mario is beating the level quickly and these obstacles impede that goal as well, but that's the whole point of obstacles so it is understandable. Every game needs something that hinders your goal or it would be no fun.. I have never seen anyone bitch about waiting for a platform in Mario, so why is it suddenly an issue in Sonic? Marketing never says that you are moving 100% of the time so that is a moot point.
If you're going to make a big deal out of having to stop, then you'd have to make a big deal out of any downtime in any game, and believe me... Every game has points where you're not doing anything, or at least not doing what the main focus of the game is. Once we take into account that this sort of thing happens in all games it becomes really insignificant. Hence: nitpicking.