Classic Shell and its analogs are all installed programs (now often referred to as Desktop apps in the Windows 10 era) and they can be removed from the computer just like any other installed program can. I generally use Control Panel, Programs & Features directly to locate and uninstall.
I so happen to have done this recently for a desktop machine that was being donated to VSDB that had Classic Shell on it.
You do not touch Windows 10 itself. Once Classic Shell is removed, the native UI reappears.
Brian - Windows 10 Pro, 64-Bit, Version 20H2, Build 19042
It is better to be hated for what you are than to be loved for what you are not.
~ André Gide