There was a suggestion at the enwiki proposal village pump (https://en.wikipedia.org/wiki/Wikipedia:Village_pump_(proposals)/Archive_125#Not-logged-in_system) to implement a top bar similar to the one on the Dutch Wikipedia for people who are logged out. This achieved a pretty rough consensus, with no negative comments being placed before it was automatically archived.
Thanks for taking the time to report this!
That's implemented via https://nl.wikipedia.org/wiki/MediaWiki:Common.js so if there is consensus, anybody with write permissions could also implement that on-wiki on en.wp.
And hence out of scope for Phabricator as this is a request specifically for en.wp and not a general change request for the MediaWiki software...