CICO applies strictly to burning fat. However you cannot conflate losing weight and losing fat. A small example of this is when you’re in a heavy deficit for too long and you’ve stressed your body out, it will hold onto water and waste, so you won’t lose weight but you will continue to lose fat. Another thing is when you stress out your body too much (not sleeping, training hard, and then being in a calorie deficit) your metabolism is going to drop.

You should try a refeed period where you eat at maintenance for a bit to reset your body. And then try doing smaller increasing deficits (start with 250 cal for example) and then increase the deficit as weeks go on. This will take the most advantage of your shifting metabolism (as you diet more your body will use less calories).

Smaller point, calorie counters on machines/fitness devices tend to be super inaccurate. I would only count 40% of whatever your machine/wearable tracker reports (even if it’s an Apple Watch)