The Doomguy/marine's previous designs, while nothing breathtaking, at least had its own uniqueness and identity to them, but I guess to modernize him they wanted his appearance to look more like other character designs from shooters you know, MC especially...
Regardless, having the Revenant or something that's been on Doom game covers before like Hell Knight or Cyberdemon on the cover for this game would've been preferable, and reached out to any Doom fan more than well... that.
Not sure why they don't just replace the front cover overall really but at least I don't have to keep looking at it when it comes out.