I've created my own controller like this:

public class TestController : Umbraco.Web.Mvc.SurfaceController
{
    [Route("{categoryAlias}/{productAlias}")]
    public ActionResult Index(string categoryAlias, string productAlias)
    {
        return Content($"Category: {categoryAlias} - productAlias: {productAlias}");
    }
}

And implemented an IComponent like this

    public class RegisterCustomRouteComposer : ComponentComposer<RegisterCustomRouteComponent>
    {

    }

    public class RegisterCustomRouteComponent : IComponent
    {
        public void Initialize()
        {
            RouteTable.Routes.MapMvcAttributeRoutes();
        }

        public void Terminate()
        {
            throw new NotImplementedException();
        }
    }

This works perfectly because when I call the path /category1/productname1 it'll return

Category: category1 - productAlias: productname1

Problem is that now it'll also choose my custom controller even if I go to /contact/email which is an existing umbraco page.

This means I am hijacking ALL of the calls to anything with 2 levels of nodes (/anything/anything).

Is there a way to make it first check if there is an existing umbraco node/path and if not then to defer to any custom MVC controllers willing to take the request. Now it seems to be the other way around.