> IMO you want to be actively trying to map the new concepts to things you already understand, and constantly working to update your mental model.

It's not an either-or.

Where SRS comes in handy is when you have to take long breaks between your study sessions (due to job + family). Have you ever tried learning an advanced math topic where you get to work on it for a few days, then may have to stop for a few weeks (or even months), then resume, and repeat over and over?

Chances are, no matter how intense you study during those few days, you'll likely forget important definitions/theorems in the periods you don't.

SRS takes care of those gaps.

Case in point - many years ago I put a lot of my intro to statistics course in flashcards and actively reviewed them. I hadn't done actual statistics for over a year, and then made a (false) claim here on HN. Someone gave me a counterexample using the chi-squared distribution. And it was amazing that I could recall the basic properties of the chi-squared distribution, and enough other theorems to verify what he said without consulting any book.

I've never used the chi-squared distribution for anything before or after.

(Sadly, I stopped using those cards years ago so I've forgotten the material!)