> Effectiveness of spaced repetition scales really fast / exponentially whereas other learning methods don't scale like that - do you agree?

Of course not. As I wrote, in the comment you’re replying to, I was a user and evangelist of SRS for years but eventually saw the reverse.

It’s a very useful tool for a certain narrow niche of memorization tasks. However, it’s an extremely inefficient learning method over the long run compared to reading and using information or skills in context.