I understant the vast majority of users do not tag artist tracks and/or the album artist.
But for the ones that do tag...
... as you said Emby will show only the "first" artist.
And this "first" is not the first as tagged. It is a random first.
I understand this issue's relevance is related to actual user Emby is seeking for.
I collect music. I have a huge collection, tag everything and would like to use Emby to store as much information as possible regarding tunes and artists.
I also would presume this is should be the user Emby developers are trying to reach.
For the ones not interested on collecting music, Spotify provides simple free music hearing services.
But I am glad you just got the idea. Improving Emby is developers team decision.
Facts are the interface provides no way to directly reach (link) ANY artist of the track being played if your scenario is a mobile/web casting to Chromecast.