It brought the Deadly Six to Earth, broke Starline away from Eggman, and has a lot of characters get time dealing with how the event affected them.
Like, Archie Sonic was 300 issues (slightly less in the main run, but a lot more including side books), five times as long, so you might be overestimating how close together events of that sort were, and a lot of the big arcs were also 'villain tries something big, is stopped'. They were at the same HQ for 175 issues. And the bulk of the time the changes and such were to side characters too- freedom fighters, and the ones who got the most changes tended to be the original ones not even from SatAM (and with the note, Sega did not care about Sally or the others, they were free-reign land just as much as Whisper). Sonic and someone might have a fight but it'd be resolved or such before long. Really not that much different than 'Eggman is Mr. Tinker for a few arcs'.
The Deadly Six were returned to Hex in a subsequent arc which again produced no real changes. Starline is an IDW original, which is kinda my point. IDW 1-50 centers on Starline and ends with his death. By comparison Archie Comics #50 ends with... Eggman himself being killed off. Sure they eventually brought in another Eggman from a different universe, but its telling. Honestly Archie is kind of a low bar, we live in the age of shows like The Owl House, the expectations for a modern kid's cartoon or comic are higher now, the boundaries more pushable.
But now in IDW Sonic, where it is really only the OCs that are allowed to actually have changing dynamics. Starline rises and falls from power then is killed off. Tangle forms a relationship with Whisper and it isn't smooth, in part due to Mimic. Clutch decides to leave retirement. Surge and Kitsunami are created by Starline, then rebel and become independent. Jewel takes over the Restoration. Belle is created by Tinker but comes to terms with his 'death' at Starline's hands. Its obvious to me that this is an adaptation by the authors, if Sonic and friends aren't allowed to change, then it has to be the OCs shook by the conflicts they participate in. They can be killed off, or find a new job, or shift their friend's circle around, in a way that Sonic and friends cannot.
Yea, there were events that changed a lot and it was more soap-opera-y, but you may be overestimating how often big status quo changes happened, and also how much was a big change to the mains, rather than others.
And, well, the OCs have some pretty good development IMO. I'm personally really digging Surge's arc.
Honestly its the soap opera-y things as much as the big ones. I know that a lot of works require you to suspend your disbelief because there needs to be tension and peril but you know deep down it has zero intention of actually killing off any of the protagonists given the genre and tone, but there are a lot of lesser stakes you can apply.
Take the whole non-arc where Sonic gets his ideals challenged and stressed. I don't really expect to Sonic go "okay then" and shoot Eggman in the head, but you could have "maybe one of Sonic's friends stops being his friend for a bit" or even "actively gets into fights with Sonic over how to handle things". The closest you got to that was Shadow, who did so over Tinker preemptively, backed down, then never pushed the issue again. The only real consequence for Sonic is the creation of Surge and Tenrec, who are 'drumroll' IDW originals, and that's just rounding out his rogue's gallery.
I'm also kinda bemused at the handling of two worlds thing with semi-canonical word of god suggesting that humans exist offscreen to the left, even though they have not appeared or been mentioned in any capacity in the IDW comics, other than the usual implicit "where did Eggman come from?" and "where did Shadow come from?". When you look under the surface IDW Sonic's worldbuilding is kind of shallow, deliberately so I suspect, as to leave blank canvass for them to fill out as they wish later. The closest we have to any sort of knowledge about the world as a whole is Cream's crayon drawing.