Well, I honestly feel like it could be a WHOLE lot better than it currently is.
One thing I love about the level design from games like Sonic Adventure, Sonic Heroes, Shadow the Hedgehog, and even Sonic '06 at points, was how open and expansive the levels felt. They had lots of leg room to run around in (even on linear pathways that led to an obvious destination), there were lots of variety among how you traversed, the levels would ascend at points, and so on and so forth. Those games felt like you were on a legitimate adventure to me, and they're really fun to traverse through.
Though, it seems like the level design is kinda following the same philosophy that was present in Sonic Adventure 2, Sonic Unleashed, Sonic Colors, and Sonic Generations. There are more corridors than ever (which are thinner than ever), there's too many sections that push you forward with no input, they're more horizontal and barely vertical, and... well, they feel way too confined and predictable most of the time. I'll admit that the footage we've seen for Episode Shadow, the level design looked... well, I kinda agree with TWIP on this one, it doesn't look the best.
Also, I have no idea why, but why have the most recent Sonic games been including sections where you're automatically running forward, and you resort to mainly side-stepping? Sonic Heroes had bosses that were confined to linear pathways that you had to chase after, but you had absolutely zero alteration with the gameplay. You weren't pushed forward, rather you had to manually run after the boss, and not doing so would have the boss charge after and attack you. You know how much more epic the Silver fight would've been in Sonic Generations, if you had manual control rather than automated control? Probably a ton.
It seems like Sonic Forces is doing the same thing. The avatar is automatically running away from the crab, resorting to you only having to press the left or right bumpers at the right time. This contradicts the nature of moments that existed with moments like the GUN truck chasing after you in Sonic Adventure 2, or the giant rocks rolling after you in Sonic Heroes.
Now, if the series actually found a way to incorporate the level design philosophies that existed before Sonic Unleashed, that would be epic.