Oh wow!!! I was having the same issues on my iPhone X(64GB). I have tried everything to delete the system data which takes up (33.4GB) of my iPhone storage making all my used storage to be (54.4GB) of (64GB), but i still end up with the same amounts of GB taken by the system data.I finally got a solution to it and I couldn’t be more happier right now. What I did was to check and confirm truly if the apps on my phone took the storage displayed by apple in my iphone storage. Truly everything was correct but I decided to delete my VOICE MEMO APP which document and data was (3.3MB) but when I checked the VOICE MEMO APP, I couldn’t find any data or files in the app which resulted to deletion of the VOICE MEMO APP. To my greatest surprise, my data storage which was initially (33GB) reduced to (6.29GB). I couldn’t believe it until I restarted my phone and checked again, I got the same (6.29GB) that the system data reduced to. Well, If I’m to bring up a suggestion, I think one of the apps already installed on iPhone is causing the problem. Just try to check and delete anyone of the already installed apps on your phone by apple. When you delete one of the apps and still get the same problem, I’ll suggest you move on to the next already installed apps until you finally find the one taking up the space. I really hope this will help someone out there looking for how to get rid of the huge iPhone storage taken by the system data. ✌️