Gears of war 4's story is so bland, and the new characters are so boring with constant quips a la all of the Marvel movies. The robots are super boring to fight, and the swarm are uninteresting in design. It's not worth it for the single player.
In Gears 5, JD is a much better character, but he plays second fiddle to Kate, who is still insufferable. It's better than Gears of War 4 though, and the multiplayer contains a horde mode with the Locust and Lambent, so you can play against the original antagonists.
Gears 4 and 5 don't hold a candle to the original trilogy, which is a shame. The new characters suck, the swarm lacks the interesting designs of the Locust, the robots are terrible to fight, and the horde mode is overcomplicated.