Yes, there are apps that are very responsive that are not SPAs. They are solving many of the problems traditional web applications have. DHH has written exten

Yes, there are apps that are very responsive that are not SPAs. They are solving many of the problems traditional web applications have. DHH has written extensively on techniques for building them, and I have written a library for building them as well. There are many problems with the client-side paradigm: security, API churn, we lose Rest/HATEOAS, complexity, etc. That's not to say that the client side paradigm is always the wrong choice, it has its strengths as well, but it is rather to say that making it the default choice, without considering the problem at hand, is foolish.