The MCU really hasn't shied away from the more campy side of Marvel. They made Ant-Man... and he had a pet ant! Strange played a battle of wits with Dormammu. Drax asked Ego, a planet whom the MCU decided to make into a Celestial, if he had a penis. I don't see how this...
...is any less fitting.
And the characters get different costumes in the films because a huge profit for Disney is selling those costumes to children and they have to be marketable designs. Target even has a fashion line of Disney inspired clothes for children, each 'season' inspired by what ever movie is big at the time, including Star Wars and Marvel stuff.
Besides, you're forgetting that the Living Tribunal didn't intervene with the events of Infinity Gauntlet, seeing what Thanos was doing as no different than war, which he considered the natural order of things. He only intervened when the use of the gauntlet began to make things unstable beyond the usual carnage that comes with an invading force taking over.
Plus Feige himself mentioned that phase four was going cosmic, and if you're going to include the multiverse, which it very much looks like they are, the Living Tribunal would be a great tool use, from a writing perspective, as sort of a bridge between the multiverse.