I was born in 2000 and didn't really know that Shadow had his own game until like 2010 or so.
Here's my opinion. One thing I want to get out of the way is that the story and themes aren't the biggest problems with the game, the overall structure of the game is by far the worse offender. The problem with Shadow's game isn't that it's "edgy" moreso that it's the wrong type of edge. The idea of seeing Shadow with a realistic firearm isn't offensive as much as it is ridiculous, it doesn't mesh well with his character design being that of a 3-4ft anthropomorphic hedgehog. Also it doesn't make sense. Why would Shadow, the so-called Ultimate Lifeform who can rival Sonic, need to use a gun? ESPECIALLY if he's fighting normal henchmen? This is why Shadow's game got mocked for being edgy, it feels less like the Sonic version of a dark themed story and more like a 13 year old's fanfiction. I hate Pontac and Graff as much as the next person, but you still need to keep a level head when writing more serious stories.