So you could certainly write your own component framework, state propagator, router, module framework, build engine, and more. But you'll probably find that, at

So you could certainly write your own component framework, state propagator, router, module framework, build engine, and more. But you'll probably find that, at the end of it all, you have a SPA framework you can share with us. If you're just doing simple web pages maybe you don't need all that, but some types of applications do.