Was Gears 2 not ‘Gears 1.5’? Are you expecting a completely massive generational leap in graphics, when the game still has to run on extremely old 2013 hardware?
343i had said they hoped to nail Halo multiplayer the first time around, so that when the next Halo came around they didn’t have to spend a ton of time improving the multiplayer and could spend more of that on the campaign. Gears already has a great multiplayer, all it needs is refinement, polish, and minor improvements to get better. Expecting it to all of a sudden look like an entirely different game is beyond reasonable.
You haven’t even seen more than a few small scenes from the campaign, and instead are basing your graphical expectations purely off the multiplayer where the graphics are usually less impressive because they need to ensure a locked 60FPS as much as possible.