You should not expect pages to be bundled in a theme. The user needs to have control over all the pages themselves.
Layouts in a theme - yes. For example if you want to provide a contact page, create a contact.html layout to be used by the end user if they want.
Regarding plugins. Check the rule in your gemspec file to ensure that the plugins directory gets bundled. And then inspect the installed theme in the site to see that it has a plugins directory.