What do you mean you miss it? What is stopping you from doing exactly that now? Plug it in, drag down the drop-down and make you phone identify as storage. Then you can copy video off it while moving music onto it, if that is what you want.
People often lament about the early days of smart phones where you could put in a microSD card to expand storage and even move apps to it. But nobody remembers the details of how janky it really was. AOSP and Googles own Nexus phones never supported apps on microSD, it was added by other manufacturers and was not perfect, often apps crashed when running from microSD or ran slowly.
I'm not defending MTP either, it's a mess too and hasn't gotten any real multiplatform improvements since back when it was first being used for MP3 players.