I'm new to C4 but so far, after 5 mins read, I can't see anything you can't achieve with PlantUML. I'm surely missing something, though.
To be honest, diagram-as-code is so powerful I can't be tempted by eye-candy. What is the game changer with C4 and all its editors (if more than this)?
The actual standard is quite light weight, which is its main selling point. The whole premise is that many teams find rigorous standards like UML and Archimate too heavy and thus resort to basic boxes-and-lines diagrams. C4 essentially says "take your boxes-and-lines and put full sentence descriptions on everything". Combine that will successive levels of detail, and you have the C4 standard.
You don't have to give up diagrams-as-code because you can create C4 diagrams with PlantUML [0] or using the C4 specific DSL [1].