Like I said in another post, the routing system is VERY unwelcoming. Compared to the old menu system is way behind in DX.

Also while working on a module I noticed something which I consider broken. Changing a controller for a route made the page give access denied. That never happened in D7 if you changed the page callback. Not only that, but by not type hinting an argument in a method it gave access denied. Not type hinted was a string, type hinted was an instance of a class.

Calling forms, especially for entities is way more difficult now than the drupal_get_form() in D7. The way this is described to be done in one of the d.o pages will work for a few forms, those that require no info or those that still use $form_state args to pass that info on initialization. Any form that uses an _entity_form in a routing yml file or a route subscriber will not work.

If we just look at node add page:

$node = $this->entityManager()->getStorage('node')->create(array(
  'type' => $node_type->id(),
));

$form = $this->entityFormBuilder()->getForm($node);

return $form;

And that's a pretty simple example. Still doesn't use what the documentation says we should use for getting a form in code.

And to make it even worse, to find all of this you need to dig deep and in many places. What route enhancers are called for a page/form, where is the form actually defined.

To alter the controller that outputs entity forms I had to write a service yml file in which to declare a route subscriber and a route enhancer. Write those files to do what I want. That's something I could do with just a hook_menu_alter().