Remove the `author` and `tags` pages

Is there any way to completely remove the author and tags pages?
I can redirect them to another page. However, isn’t it possible to disable theme somewhere on Ghost?

You can remove them from the routing file (routes.yaml - access it through Settings > Labs). But be warned that many themes link author names to author pages and tags to tag pages, so you may be creating a bunch of broken links, depending on the theme…