With the media interface, you have full control of the media device (eg iPhone) through COMAND and your steering wheel controls, and the track information is displayed on COMAND and in the instrument binacle, and maybe even artwork (cover).
If the auxiliary port works, then you can plug in using the device jack socket, or better still plug a Bluetooth receiver into the auxiliary port, and then control it using the remote control which comes with the Bluetooth receiver, or by voice/watch if that’s your preference.
I can recommend the Anker SoundSync as a Bluetooth receiver. If you search this forum you’ll find information I’ve posted on it before.
PS I’ve had several Mercedes with auxillary sockets and all of them have been a bit temperamental, requiring a wiggle, but not to the degree you describe. Perhaps it’s a well worn hole which has been stretched in the past through use and abuse, hence it doesn’t seem like it’s in properly. Ahem.