Actually the remote entity lets send command with command in plain text, so it depends on the integration. Whereas the media player entity has common commands : play/pause, previous/next…
Therefore to have a card or make script requires to map all the commands manually.
Most remote controls have common buttons : arrow keys, OK, back, menu (main or popup/options menu), exit.
It would be great to have predefined commands advertised through features mapping so that one could design a card without any additional work