Under what merits has The Dark Knight been topped or hasn't yet by the MCU?

To clarify really quick, I don't think the first Avengers film and Infinity War tops The Dark Knight on artistic merits but as a comic adaption. They don't necessarily tackle major human themes, which is fine. All great films don't need to always have a theme to it. I think The Avengers tops TDK for being one of the first successful superheroes assemble film and Infinity War for going all out and building it up for 10 years and delivering one of the most compelling story and villains since Heath Ledger's Joker and even rivals his performance with a slight nuance to it. Thanos was a refresher from megalomaniac villains, or world-domination villains or tragic villains, or revenge-seeking villains, or "just for the evulzs" villains like the Joker. He was just a guy with the goal that had nefarious intentions and he succeeded and then just walked away. He didn't care for ruling. It was refreshing.

On the other hand though, ...

Winter Soldier and Civil War both have artistic merits and good character depths and good themes you can really analyze and break down, particularly good vs. right, utilitarianism vs. deontology, government surveillance vs. oversight, all relevant to the human condition in a somewhat original way. The Winter Soldier shows how corruption and extremism poisoned an organization until it was unsalvageable. It also lays out Cap’s principled, right-and-wrong mentality with the complexities of the surveillance state and political espionage, which even by today's standard is a political hot topic.
And Civil War continues that, but slightly adjusted, covering government oversight and collateral damage and accountability, but within a superhero world, but even then with world's power and military and the collateral damage they leave (drone strikes), is still a political hot point today too. And with Cap against Stark in an ideological conflict, rather than it being a good-versus-evil story, it's a good-versus-right in which both sides have sound arguments behind them where neither of them are necessarily wrong or bad on the surface, but their actions in pursuit of their respective ideals become questionable. And that leads to another lesser more vaguer theme, but family breaking down. To quote Zemo, "An empire toppled by its enemies can rise again. But one which crumbles from within? That's dead forever."
These are all very much strong themes with related to the human conditions.

Here's the thing though...

They are also comic book movies as well and embrace the comic elements to them, which a lot get hung up on, especially with any type of humor to it and you automatically label it as silly and fail to see the real message behind them. It's just more subtle and subdued and not on the nose like The Dark Knight does it and that's why Civil War and The Winter Soldier really top The Dark Knight. Nolan did everything in his power (and he did successfully too without being pretentious) to make it not look like a comic book movie but more of a thriller/psychological movie.