Is it possible to disable a content type?
You can't disable a content type, but you can prevent (almost) everyone from creating/viewing/modifying etc. an Article it with setting the permissions accordingly.
If there's no Article content on the site, it's 100% safe to delete it. (It's interesting to check out how the default and minimal installation profile provide different sets of content types. Article is just a "stock" content type which is by no means necessary to have.)