The two new Gears games play pretty much exactly like the old ones imo. I think it's just the formula is stale now. I feel the same about Halo. It didn't get worse so much as it didn't evolve at all to compete with the new games coming out. Eventually, you need to wrap shit up and change the franchise, kind of like how Assassin's Creed completely reinvented itself with Origins by leaning into the RPG aspects of the game and veering more toward a Witcher 3-esque experience than sticking with the tired and tedious gameplay from previous installments.
Gears is still Gears. It's just that hiding behind chest high walls and shooting wave after wave of enemies with the same ten weapons from the original trilogy isn't as exciting any more because other games are out that are better now. Adding a semi-open world and a couple of side quests didn't change the basic loop. It just made the game a little more tedious.
I'd also say that PS exclusives were generally better during the PS3 era too. Microsoft was more competitive in that regard (and had a vastly superior controller), but it was still Sony's show.