Spaced repition aids both parts of this so not only is the information stored it's also easy to retrieve.
The way it does this is to open a firehose at your memory. If the information is simple and well presented, then ideally about 90-95% of it will stick.
If you want to retain 1000s of items (like a foreign language) and can accept some amount of loss, then spaced repetition is effective.
But it's not designed to increase the relative chance that any individual item will be remembered. If you want to learn a small number of items with 100% recall, then spaced repetition is a bad way of doing that.
You're talking about what it was designed to do, I'm hypothesizing about what it's actually doing.
Ebbinghaus demonstrated that spaced repetition is what causes people to memorize things, using nonsense words for exactly that purpose, to ensure that there was no possibility of any sort of 'clicking' or semantic processes. Just pure memory based on repetition either massed or spaced.
I've worked on this for a while. I've written several different memory programs, for helping to review and memorize things. I have some thoughts that may help you feel better:
In the end, spaced repetition is not what causes people to memorize things. You can review an object over and over and over......50 times, or a hundred times, and still not remember it. Other times, something will click in your mind, and you'll remember it the first time, without any repetition.
My hypothesis is that repetition merely increases the chances of your brain being in a state where it will remember the thing you are trying to remember. And certainly there are things you can do to increase the chances of it sticking.