You probably don't need a single-page app, right up to the point where it's a business requirement and you have to translate a GB worth of convoluted JSPs into one because the client likes smoothness in their flows, continuous saving, and all those nicely choreographed state transitions you just cannot get without having a framework hijack the History and File APIs from the browser's paws. Yes, a nice state machine-l…
Website != Browser app != Mobile app != Desktop app != AR/gaming platforms
If you know which of those you need, you can make an optimal technology decision. No one can expect to turn a wood-framed structure into a steel-framed structure. Nor build a steel-framed structure for the price of a wood-framed one.
In this day and age, chances are better than not for anything reasonable involved, that this smooth interaction is a business requirement, but YMMV.