How do I create a local menu action to node/add/page?
Basing on this comment found on Local action links now provided by plugins using YAML discovery and implementing LocalActionInterface, this is the action declaration you should use.

amidori_utils.add_content:
  route_name: 'node.add'
  title: 'Add content'
  route_parameters:
    node_type: 'blog'
  appears_on:
      - view.admin_blogs.page_1


I take that, in your case, node_type should be simply blog, if that is the machine name for the content type you want to let users create.