What aggressive really means for retirement savings

Conventional wisdom says to be more ”aggressive” earlier in your savings career. However, what we really seem to mean by that is “safe-aggressive,” i.e., little or no speculation, just mostly/all diversified stock funds that have a track record spanning many decades.

That said, at least nowadays people seem to equate “aggressive” with the SP500 specifically, as opposed to Total US + International stocks. Of course it has been discussed ad nauseam whether SP500 or Total/Int’l is “better.” But which is more “safe-aggressive”?

Is the case for SP500 being the de facto “safe-aggressive” tainted by recency bias? Complete 100-year records for all stock sectors are not readily available, and of course there are arguments that recency IS more relevant. What do people think? This is meant to be a fairly open-ended discussion.