he PSR-4 standard requires your files and directories to be case sensitive and the corresponding classes and namespaces to be in PascalCase.

For a App\Controllers\BaseController class, the file should be located in:

app/Controllers/BaseController.php

Notice the uppercase C

2nd error: For any namespace after the top level namespace, there must be a directory with the same name.
You have a App\RoutingDispatcher class that should be placed as app/RoutingDispatcher.php but the app/routing/RoutingDispatcher.php file would correspond to a App\Routing\RoutingDispatcher class.
You must change the namespace of that class or move the file.

If you change its namespace, be sure to rename the app/routing directory with a leading uppercase letter.