For sure the Adventure games have plenty of other issues as well (mostly SA1, which is almost as hilariously busted as '06)... but the core controls are also just one of those things, and were definitely not some strong point that the series should be looking to return to.
I did somewhat exaggerate the whole "flying off the stage" stuff, as that's not as common as I probably made it sound. I was mostly just using that as a way to illustrate that the controls, and the way the games handled momentum is bad from a fundamental gameplay standpoint. It doesn't really matter if the width of the levels mean that when someone's struggling to control Sonic, they don't actually die... the point is really that they're consistently struggling to control Sonic. I can load the game up now almost two decades from its original release, and I'll still probably pinball may way around the opening corner in Emerald Coast... which has ribbons there tellingly, because basically everyone will. This is also why I take issue with claims that the levels in the Adventure games were better designed. It takes damn near an act of god to play through pretty much any level as Sonic and not be constantly running full tilt into obstacles, because they constantly do crazy shit like following up a long straight slope downwards, with a fucking square U-turn at the end (thinking specifically of Sky Deck here).
If Sonic moved at the speed of Mario, then the controls employed for Sonic Adventure would be great. He doesn't though (and shouldn't imo... just play Mario for that), and so the controls are a goddamn mess.