Great question. This was my concern initially, but I’ve found it isn’t a big deal in real life. And many have posted online that their concerns about designers were unfounded.
I’ve worked with designers in both Angular and React’s paradigms. Both have a small learning curve for designers, so either approach works fine from their perspective. In Angular, designers need to understand Angular-specific things like ng-repeat/ngFor and so on. In Angular 2 inline templates, they also need to understand that the markup sits in a variable called ‘template’. In React, designers need to understand that the “HTML” is in .js files in a render method and a few minor differences like className and htmlFor.
In either case, designers adjust quickly. Many especially appreciate the intuitive nature of breaking the UI down into small components. The component model isn’t just useful for designers — It makes it much easier for the designers to understand the bigger picture as well.