There are also the so called "universal CMS", which are headless but with a frontend SDK to achieve the same WYSIWYG, but with a modern frontend framework and deciding exactly what content editors can do. See for example React Bricks.
Or you can have a look at React Bricks, too.
Devs create content blocks as React components with inline visual editing and sidebar props, with constraints so that the design system cannot be broken.
Content editors can use these Lego bricks of content with freedom, without breaking the design.