Yes. Sonic is limited on small or multi-layered stages.... Kinda.... it definitely feels like it due to the fact that he can't unleash his full speed to overwhelm and pressure his opponent; well, he can, it's just much harder. Your opponent can hide up on or below platforms or on the other side of walls creating an obstacle which you have to slow down and navigate around. It makes your approach more predictable.
On the other hand, for Sonic, at least in Battlefield, his Usmash will hit people above him on platforms; so abuse this. Also, forget trying to drop through the platforms, just run off the sides of them; use an Nair if you feel like you need to cover your descent, or use Spin Charge. If they're on platforms above you, abuse your Up Smash; Or get them away from the platforms, push/throw them to the stages edges and fight off stage or follow them up in the air for a juggle, platforms make it easy for you as well. When you're both on the ground, short hops are your friend.
So Sonic can do just fine, you just have to play a little differently.