So, two readings here, what skill does a DM need high level abilities at, and what is the most important skill for “high level DMs”. So two answers…If you had to pick just one skill as the single most important one for a good GM to have at a high level, what would you pick?
The most important skill for a DM to need high level abilities at is the much mentioned, reading the room/communication/knowing what your players want, AND adapting to that. You need to run the type of game the group wants. That’s not something they can tell you, this game and how you will play it with your players is a relationship and develops over time, it’s a conversation, of both words and methods, and you figure out what works best for everyone.
Once you figure out and settle into the way y’all like to play, then it would be narrative and performance skills. Making walking down a corridor more than just walking down a corridor.