I'll be honest, I think the game is going to turn out alright. Not necessarily a masterpiece, but not as bad as everyone's making it out to be, and hopefully not as bad as Sonic 06.
The game retains the basic gameplay from Sonic Generations. That game was widely praised. I mean, yeah, the addition of the OC and the "edgy" tone the game seems to have going for it might make some people roll their eyes for targeting the DeviantArt demographic, but I don't see where this immense hatred is coming from.
I admit, though; this probably won't be as good as Sonic Mania. I don't think any modern-day Sonic game can top that. But that doesn't automatically mean Sonic Forces will be bad.
Personally, I don't see myself fitting into the demographic for this game. The game seems more story-oriented than previous recent Sonic titles, and I only have a fleeting interest in Sonic storylines these days.
The whole Sonic franchise is weird and amalgamated. There have definitely been ups and downs throughout the franchise, and what seems to work beautifully in one game gets totally bashed upon in another (or heck, even just a port of the same damn game), and what Sonic fans expect from a game seems to shift from year to year. Critics seem to continuously flaunt the "fact" that all modern Sonic games suck, even though there have been quite a few good ones after the classic era (the Sonic Advance series, the Sonic Rush series, Sonic Colors, Sonic Generations, etc.), though I suspect this is more due to the combination of series ignorance and the unwillingness for any reviewer being caught dead liking a Sonic game, especially considering his "uncool" status among gamers of late.