> "C is one of extreme cases"

I would say it's the other way around.

We've had the knowledge and tools to build performant, scalable and highly maintainable systems for a while now. The learning curve is there, but that's part of the trade. We've been too occupied with reducing the entry barrier though - the end result being people shoving JSON into places it should have never been in.

JSON can absolutely be a part of a text editor's architecture - with areas that don't necessarily require near real time performance (think configuration, metrics). Anything beyond that - C structs would be a great way to go, and I don't see why there's a debate here.