Understandable, as Knuckles Chaotix was shit.
It seems to me like Sonic, as a series, falters whenever the devs try something
new. This rule has held for the past 30 years. People loved Sonic 1, 2, 3 (& Knuckles), the Sonic and Shadow stages of SA1/2, the Sonic stages of Sonic Unleashed, Sonic Generations, Sonic Colors, and Sonic Mania. However, Knuckles Chaotix, the non-Sonic/Shadow stages of SA1/2, Sonic Heroes, Shadow the Hedgehog, the Werehog stages of Unleashed, the Wii games, Lost World, and Forces all got shit on.
The Sonic Handheld games and Sonic '06 were generally disliked for technical and design problems that interfered with the gameplay, rather than the design of the games on paper.
We may look back at Sonic Adventure 1 and 2 with rose-tinted glasses, and, in a way, they were great for the time period. I've been playing the SA2 port on Steam lately and it looks surprisingly great on my Ultrawide.
However, back in the day, reviewers bitched
constantly about SA1's fishing stages, and how SA2 had clunky controls on the Tails and Eggman stages, and how the camera got in the way of navigating the more freeform Knuckles/Rouge stages. You could rotate the camera with the triggers, of course, but it would still fight you.
It seems like Sonic is at its best when it doesn't stray too far from the original formula of high speed, springs, and loop-de-loops, regardless of whether it's in 2D or 3D. Most of the games in the series that have escaped harsh criticism are really Sonic-focused and don't try and give us any extraneous gameplay archetypes beyond that. When they do make the mistake of focusing too much on characters other than Sonic, or having Sonic do something outside his usual milieu, reviewers drop the hammer on them.
Sonic Frontiers is going to be an open-world game, supposedly with parkour-style navigation of the environment. I'm cautiously optimistic about this, but I also know exactly how this concept could fail. I say this with a caveat; I love open-world games. I have played the shit out of Elder Scrolls, Fallout, GTA, RDR, Far Cry, and so on. I'm well aware of the strengths and drawbacks of this style of gameplay, and there are a number of reasons why an open world could be a poor fit for Sonic.
In most Sonic games, the levels are pretty linear and self-contained. The gameplay revolves around discovering shortcuts in the stage and memorizing them so you can cleanly make use of them on every run. To some extent, this is also true of Halo, and it created some problems for Halo Infinite. Halo, like most linear FPS games, is about memorizing weapon locations, shortcuts, enemy spawn points, et cetera, and developing enough discipline to clear a level quickly and smoothly regardless of the difficulty you're playing on. The linear gameplay of Halo creates opportunities for "set-piece battles", just as the linear gameplay of Sonic creates opportunities for tricky bypasses. Open-world games are stochastic by their very nature. You can approach an encounter from any direction, and it completely changes how everything plays out. The closest thing to linear gameplay in an open world is to plop big floating holographic checkpoints in the environment (like races in Grand Theft Auto) and have the player run through them in a specific order, but this always feels like an artificial constraint imposed upon a level with limitless possibilities, and it ends up having randomness anyway because of what happens
between those checkpoints.
So, that's problem number one. Open worlds, unlike linear stages, are too random to be "learned"; instead, players develop a general set of techniques that fit every possible scenario. This means developers often feel like they have an opportunity to be lazy with the level design, plopping a few buildings here and there with a great deal of nothing in-between.
This brings us to problem number two. People see screenshots from Frontiers, and they're like, "wow, the graphics look amazing!":
I see it, and I wonder why the hell Sonic is now in friggin' Zelda, or on a Halo ring or something, and what he plans on doing, gameplay-wise, while traveling through those empty-ass forests between those moss-encrusted Forerunner ruins.
Sonic himself is too fast for an open world of modest size. Most open-world games are artificially made to seem larger by limiting the player's access to vehicles and limiting the player's run speed. The only exceptions to this rule are superhero games like Prototype or Infamous, and with games like that, it is very often the case that the player will bypass large swaths of the environment without even bothering to take a look around. This often means that devs don't bother detailing the environment too much, or if they do, much of it goes unseen.
Sonic eats up the environment like nobody's business. People have modded Sonic into GTA games before, which gives us a perfect visualization of the problem of Sonic inhabiting an open-world environment:
At this speed, there is no reason to pack the environment with detail because no player will ever see it. They'll just run right past it. There are a couple ways around this. One is to make the entire map proportionally much larger than in a typical open-world game. The other way is to slow Sonic down, like when he's in Station Square in SA1.
Admittedly, game engine tech has marched on, and LOD pop-in isn't as bad as it used to be. In like, UE4 or UE5, you
can make a Sonic game with a huge environment, and have Sonic traveling at - or close to - his full speed without much trouble. However, there are tradeoffs. It's a balancing act between depicting Sonic at full speed in a huge, inflated, empty environment, or slowing him down and actually bothering to populate the open world with detail, obstacles, et cetera.
Then, there's problem number three. Sonic has a fairly limited, standard set of traversal moves throughout the series. The Spin Dash and Homing Attack, for instance, are as much attacks as they are traversal techniques. In Sonic, moving and attacking are the same thing. Sonic destroys enemies by crashing into them with his body, which is a holdover from the early platforming era when Mario used to stomp Goombas by jumping and landing on them. This is different from a lot of other adventure games and platformers, where movement and attacking are two entirely different things. While playing as Sonic, an enemy is not something you slow down and fight with a sword or gun or fisticuffs or whatever, usually (with a few exceptions). They're just another type of obstacle. The attacks are dual-purpose. There are spots in SA2 where using the homing attack for traversal is basically mandatory, like in some spots where you use a homing attack along strings of flying enemies that act as stepping stones, or in Final Rush when you have to use it to ascend short vertical rails:
Every adventure/platformer character has their own type of traversal moveset. Lara Croft specializes in ledge grabs and ledge traversal, slide-into-jump maneuvers, crawling under obstacles, hand-over-hand, swinging, et cetera. The titular Prince in Prince of Persia can bounce all the way up two opposing walls, wallrun, et cetera. Sonic doesn't do any of that. Those types of maneuvers usually require slow, careful planning, standing in place and eyeballing the jump before you do it. In Sonic, there is no time to eyeball. You do a homing attack on a spring, and sail through the air, and now you can come down on a platform somewhere well above your previous position. If the environment is made too complex, and Sonic's new moves cater to that, it will only slow things down. That's why, in games like Prince of Persia, or Titanfall, or Mirror's Edge, when you're supposed to do a wallrun, you'll usually encounter a conspicuous wall or billboard or something that looks like you're supposed to wallrun along it and then jump off. When it comes time for Sonic to do a wallrun in Sonic Adventure, the ground itself twists into the vertical like a fucking Hot Wheels track, no reflexes or planning required.
Designing an open world with traversal mechanics and/or adding new moves to Sonic's repertoire could slow Sonic down much more than if he was confined to a fairly linear track, if they allowed it to.
I want to see what they'll do to avoid these problems in Frontiers. It is honestly a real design challenge to make an open-world environment with good platforming and verticality that isn't flat and boring, or rendered monotonous by excessive backtracking, and that goes double for an open-world game with a really fast player character.