Honestly speaking, Sonic Forces just... didn't do it for me. The gameplay absolutely killed any momentum of enjoyment I had for anything in the game. Classic Sonic is arguably the worst part in the entire game, serving no plot significance and having some of the absolute worst levels in the game. The Avatar is too clunky for me to properly enjoy, though the character customization is probably the most well thought-out idea in the entire game (not saying much to be honest). Modern Sonic was the best gameplay style but the lack of guard rails in most stages with some pace breaking 2D sections (along with the hideous jump that all the characters have in the game that can either make the character feel too light or heavy) made it hard for me to revisit.
Overall, I just, I wasn't a fan of this game. The music relies way too much on synth for me to properly enjoy the soundtrack (there is a good soundtrack here, just a change in instruments would be for the better); the plot is muddled with actions of characters that have no weight or significance to any of the events (for literally five minutes the game goes from "oh boy, Sonic is gone?!" to "Oh wait, there he is!"), resulting in probably one of the better plots we've seen since Sonic and the Black Knight (then again, it's not saying much); and the visuals are okay, but half of the stages are just reused assets from Generations and Lost World.
I just cannot find much enjoyment out of a mediocre attempt of a game, even if it's meant to be essentially a parody of older Sonic games with its use of buttrock and OCs. If I had to give it an arbitrary score, 5/10 seems fitting.