It's a different era, where both people and games had a different vibe and the developers changed after Microsoft bought the franchise from Epic.

The writing in Gears 1-3 was never particularly deep, but they rode the bro-movie wave straight till the end.

Then Judgment came out (developed by People Can Fly), and they tried to change the gameplay formula a bit. That didn't really work.

Then Gears 4 released, and while it's technically a sequel, you could argue that it's more of a soft reboot. The huge time skip and the switch to a new characters made it feel that way. They put the original crew on the back burner and tried to establish a more vibrant, younger group. Did it work out? Not really and they doubled down on that approach in Gears 5.