Indeed, you're right about the limitations with DirectX on Windows 7. Unfortunately, there's no official workaround to get full DirectX 12 capabilities on a Windows 7 system. DirectX 12 was built from the ground up to provide a significant performance boost and better efficiency on modern hardware setups, features that just aren't backported to Windows 7.
Upgrading to Windows 10 or later would be your best bet to take advantage of DirectX 12. It's like expecting a floppy disk to store a Blu-ray movie; sometimes, you just need to make an upgrade!
So while it might be a bit of a hassle, think of it as stepping into a modern era of gaming performance!