The design is indeed proprietary. This makes sense for the business to maintain brand integrity.
Vue was great! Loved not having to go all in on build tools, you get everything just by dropping in a script tag. I think Vue is perfect for websites where you just need to sprinkle in some more complex frontend components.
If you’re building a front-end app (think gmail) then React makes more sense to me. Also depends on how many people in your team I guess — I was writing all the code for this project, so the simpler the better.