Spaced repetition is the way your brain stores everything, even abstract ideas, mathematics,etc. You can only remember anything either by having repeated exposure to it, or having it really connected to some other memory of yours.

Also, you seem to underestimate the importance of having encyclopedic knowledge. I agree that it is not useful to have random facts in your mind, but passive knowledge is extremely important - like even on topics you are not well-informed about, having learnt something about it in the past will put you in a much more open-minded position on it. If people were to remember some really basic biology from high school, they would be much less open to bullshit like “alternative medicine”,anti-vaccines, etc.