I'm going to do my best to describe why I don't like the automation that 4 has brought on, with its level design and why I will never accept it as a 'classic' despite Sonic CD being tied to it which I still think is a cop-out.
...damn that's some classy music you chose.
With the boosters in the original games they were simply boosters for extra speed and always changed up slightly in how you approach them. They were never an escape from danger either because it was just there to make you go faster. If you go too fast in Chemical Plant Zone you can lose rings or possibly lose a life, or if you take too much speed in the big..er....candy-cane-colored tubes in Carnival Night Zone, you'll possibly propel yourself too far once hitting regular ground: go too slow and you fall below it and miss the path entirely.
If we're going to go a step further, some levels didn't rely on boosters but the level design to make you fast. Go on the UTMOST top path in Mushroom Hill Zone Act 2 and in the end when you have a million loops, you'll probably rocket out of there faster than any booster could ever hope of doing. Why? Because that's what BLAST PROCESSING IS BABY.
...and even then, the things with all of those speedy sections is you're always forced to pay attention because if you don't you could screw up be it any kind of trap or insta-death. YOU DON'T KNOW and if you do, sometimes you can mess up because to err is human. That goes for all of the classic "Saga" of Sonic 1, 2, CD, 3, and Knuckles.
With Dimpsification and speed boosters, the level is the only trap you have to worry about: not cleverly placed or designed traps or enemies: just the level itself. 9/10 of the time there are enemies placed immediately after speed boosters because you automatically destroy them for free points (And it's usually 3 or 4 of them, back to back). What's more, is it's not speed that's added: it's just one constant speed and it doesn't even look that fast. It's boring to watch and it's handholding to players afraid to learn how to deal with badniks outside of easy combat (Press A to kill everything, of course), unless they're going to homing attack it then.
With Dimps I don't feel like I'm playing Sonic levels with badniks: I just feel the badniks are sorta 'there' and are never a part of the stage.
Sorry. I HAVE to make that point clear.
They're just booster or ladder fodder and MAYBE placed randomly. Don't you remember the first time you were in Lava Reef Zone, and saw that badnik you couldn't kill but he started to glow? Once he exploded you either were like "OH " cuz you lost your rings or "Holy crap, better make sure I have a shield or be Super/Hyper each time I come across him" because you were usually in tightly-close spaces on most encounters.
Or how about ANY story on your encounter with ANY of the badniks? There's hardly anything to really say about those in 4 due to them just being booster fodder or being easily taken out by the homing attack cuz they don't really pose a threat.
....sorry that's slightly off the topic.
Tl;dr version: Original ways the level designs gave you natural boost where you could take and do with what you pleased immediately after given a boost: new way is extremely hand-holding and doesn't even add to speed, it just maxes out at one.