Part 1 of 3
This is not what you want to hear but needs to be mentioned just the same
System Data technically, has a mount point /System/Volume/Data
With a mount point of /System , this Volume is part of the Operating System.
It is where your User Account (s) was made when the computer was First Setup as New
We can point-out what may be included in this Volume much like @muguy has already outlined
Though, how to reduce this is a long and complicated trial and error process
This process does not always prove fruitful
Part 2 of 3
The more popular way to address this issue is to Start Over from Scratch
For Apple Silicon computer >> Use Disk Utility to erase a Mac with Apple silicon.
For Apple Intel computers >> Use Disk Utility to erase an Intel-based Mac followed by How to reinstall macOS
Always make a Time Machine Backup before proceeding
It is also suggest to Only Migrating the User Account and nothing more.
Emphasis on User Account Only
Reinstall the Needed and not the Wanted applications from the Apple Apps Store or Directly from the Developers
Part 3 of 3
From what I have seen on these Forums
93.72 GB in System Data seems to be about normal for some but not all
Generally when this issue is discovered by the User ( you in this case )
It is because the Internal Drive Capacity of this computer maybe on the small size
Meaning, the computer has a 256 GB Capacity Drive
Sorry but running a computer with a 256 GB Capacity Drive in 2025 is akin to when Apple Sold the tiny 128 GB drive for the Entry Level Laptops
It all sounded great at the time but given some years later the Users Needs for additional storage has grown
On you next purchase, make a Custom Purchase and Spend the Extra Money Up Front on a larger Drive Capacity Drive and add more RAM
This may Future Proof the computer for your growing needs for storage
