The levels were design the way they were because of time travel. If they just made stages more linear and closer to traditional 2D Sonic stages, the time travel gimmick wouldn't be so pointless as it is easy to gain momentum in any non-CD stage. Because of this, they encouraged exploration by making you find half pipes or double springs to time travel on.
I think it's a bit of a failure that a mechanic involving continuous speed in a Sonic game has to be activated by bouncing back and forth between two springs facing each other. It works well when it's a speed area like a tunnel that launches you in the end and lands you next to one of your past objectives, but those are more the exception than the rule.
My friends and I just talked about this game as well as Sonic 2 on our podcast if anyone wants to give it a listen. There was also a good amount of discussion in the Genesis/Mega Drive community thread.