It's a mistake to believe that a game can only really change with the discovery of "advanced techniques" or with sweeping changes such as custom movesets, unless your actual intent is you want the game to change in a very specific way. Knowledge, experience, and familiarity are such important factors that the game will inevitably change whether we want it to or not. It's all but inevitable, and the only question is in what direction it might change.
Related to that, I've seen an incorrect sentiment that existed back in Brawl, with Smash 4, and even games like Pokemon and Starcraft 2, which is that, because there are more people participating in a competitive environment compared to when a predecessor had come out, players should be able to figure out almost entirely the inner workings of a game much more quickly. While this is true to an extent, in the sense that more people working on something will yield faster results, there really is no substitute for TIME. You can have the deepest theoretical knowledge and the sharpest analytical mind, and still not be able to grasp what a game will become, because the process of actually playing and going through years and years of learning will always be a factor.
Also, going ham is not the optimal choice in a lot of different games, and I don't think it's inherently a fault of Smash 4 if the game doesn't turn out that way. I was listening to
Ultrachen yesterday, and they mentioned really enjoying watching Smash 4 at Apex, especially Abadango vs. Dabuz, because of the emphasis on positioning. See their further thoughts
here.
And even if people find a way to play much more aggressively, in some cases it'd be kind of difficult to tell the difference between aggression and defense anyway. What does an aggressive Olimar do? Run around and throw Pikmin. What does a defensive Olimar do? Run around and throw Pikmin.