10 - 15 seconds to load a page is the result of poor code rather than 'because it's a client-side app'. Consequently you need to compare a poorly built client-side app with a poorly coded server-side app, or a poorly configured cache, for it to be a fair comparison. And, sadly for us all, there's every chance it'll be just as slow if was rendered somewhere else.
The answer to slow pages is to build them better no matter what tech is being used to drive them.
In the case of this page specifically, loading 17.3Mb of gifs is the main problem.