The point is that complexity is something that is not being added to the former base model. It's just a steady gain of unnecessary features. Another example would be the Pokémon games, which gained - in the latest one - the ability to make bread and that was about it. Oh, and a bunch of other Pokémon.
Pokemon is actually an interesting case when it comes to relative standards between games.
First of all, Nintendo is not counting on the same demographic playing all of the games in the pokemon series. They therefore have little incentive to make significant improvements or changes, and are instead biased towards repackaging a shinier version of their product for the next generation. Features like poffins (pokemon breadmaking) add a minigame but don't change the core gameplay that is still novel to their desired demographic.
In addition, as a competitive pokemon gamer, I would say that the evolution of the portions I care about has not been an unsubstantial or unnecessary one. Certainly complexity of pokemon battling has increased over time. However, I think that most competitive pokemon players would agree that the changes to the battle mechanics of the game (gen 2: held items, special defense; gen 3: better held items, abilities, vastly increased customizability of pokemon through EVs; gen 4: physical/special split, rounding out of held items introduced in gen 3) have increased the entertainment value and deepened the battle system.