SRS is really good for learning small, compartmentalized knowledge items. Its usefulness degrades quickly when you move from knowledge to concepts. I'm currently learning Japanese and using several SRS tools to do so. The ones that work the best are for characters and vocabulary. I also use one for grammar, which is okay-ish but doesn't translate as well to the SRS format.

So in the context of programming languages, SRS might work if you need to memorize method names or method signatures (though I don't see why that is needed in the age of autocompletion and instant lookups from inside the text editor), but not so much for fundamental language concepts (like "how do lifetimes interact with the borrow checker").