Note, I'm not saying complexity is bad. Look, I ADORE wargames. I spent way, way too many hours playing things like Star Fleet Battles, so, I'm absolutely no stranger to complexity.
And, obviously, something like 5e D&D is a LOT more complex than some one page RPG. Which does not make 5e a better game at all.
The point I'm trying to make is that within a given game, so, only looking at that specific game, each iteration of that RPG will be simpler and more streamlined than what came before. I'm really struggling to think of an RPG that increased in complexity over time. Although, I suppose you could argue that within the lifespan of a given iteration of a game, complexity does increase as new sub books and rules are added. So, sure, you start with basic 3.5 E, which has a complexity of X. Then you add a bunch of splat books and supplements, and that complexity goes up (sometimes by a LOT).
But, once a new edition rolls around, the baseline of complexity trends downwards each time.