Even though there’s been an abundance cosmic goodness in the MCU, we’ve yet to see some of the more abstract mysterious beings like Eternity. That almost changed back when Avengers: Infinity War was still being written, in a draft where the screenwriters introduced the Living Tribunal during the big fight scene on Titan. According to writers Markus and McFeely:

MARKUS: We did try to put the Living Tribunal in the first movie. We wrote a scene in which he appeared during the Titan fight. And everyone was like, what?
McFEELY: Whoa. He’s got three heads. It would indicate a whole different level of architecture to the universe and I think that was too much to just throw in.
MARKUS: The idea’s still in [Marvel Studios President] Kevin [Feige]’s court.
McFEELY: Oh sure, we probably just spoiled it.
MARKUS: The Living Tribunal has his own streaming show.
McFEELY: It’s like “Judge Judy.”

The decision to initially introduce the Living Tribunal on Thanos’ homeland is telling that Kevin Feige may be saving for him for the highly-anticipated Eternals film. The sequel to Doctor Strange is also a potential film to debut the character in as they’ve already referenced him in the first film. I’ve always felt like they should have debuted some of the bigger abstract entities in Avengers: Endgame as a way of dealing with Thanos’ snap on a truly Marvelous cosmic scale.

Source: NY Times