That's not true. Sonic Advance 1 was the only Advance game that tried to be classic, but Dimps has always been bad at level design even back then. Advance 2 changed the series into hold right downhill speedrun, and Advance 3 is a mess. The Rush games have even worse level design and introduced the boost mechanic that's been overused and terrible physics that Sega borrowed for Generations and Forces. They're good games overall but basically ended any hope we'd get good classic Sonic games.
Dimps level design, especially from Sonic Advance 2 onward, is very automatic with lots of springs and boostpads to send you in the right direction, tons of bottomless pits, and very sterile visuals as if every level was made of Chemical Plant Zone tubes and levels with very little distinctiveness beyond visuals.
People have complained about Dimps since Sonic Advance 2, but instead of fixing their level design Sega just started adding these to every game: