First, there is no need including the Route files in the $routeFiles since the modules are autoloaded and the Routes auto discovered.

But in each of the custom module config path, I included the Services.php file and in the Routes.php files, I brought back the former routes settings with the appropriate namespace to each of these files

in BudgetingModule\Config\Routes.php file

    namespace BudgetingModule\Config;

// Create a new instance of our RouteCollection class.
$routes = Services::routes();

$routes->setDefaultNamespace('BudgetingModule\Controllers');
$routes->setDefaultController('Index');
$routes->setDefaultMethod('index');
$routes->setTranslateURIDashes(false);
$routes->setAutoRoute(false);