All of the websites that my team at the Government Information Center manages are built in WordPress.
In late 2018, WordPress changed its content editing interface from the classic editor to the block editor AKA Gutenberg. We started the process of converting client websites from the classic editor to the block editor, which is still in progress.
We have an eye on experimenting with the theme.json functionality to use for a design system. This file will allow basic styling configuration for multiple elements in JSON format, and it will be easily deployable to multiple websites that use the design system.