Updated: 27 January 2023
The macOS Finder provides an option to control the display of document icons; this is either the icon provided by the application (or the system, if the application doesn't provide anything suitable); or a "thumbnail" icon generated from the file's contents.
The Finder's "Show icon preview" option (in the View Options panel) controls this behavior. Here's what the icon view looks like with icon previews turned on:
If you would prefer to see the system default icons (which have the application icon superimposed), you can turn off "Show icon preview":
The "Use as Defaults" button establishes the current view settings as the Finder's default behavior.