I have a theory that maybe Thanos's goal was actually to delay or stop the Emergence in several planets. He knew that, if a planet's population grows too big, it generates the necessary energy for Celestials to hatch out of a certain planet. Maybe that's what doomed Titan (a bit hard to believe given Titan is not utterly destroyed, but rather just left mostly wrecked, maintaining its planetary integrity, but we don't know at which extent does a celestial birth affect the integrity of a planet... we know it "destroys" it). Maybe Thanos's goal of halfing the universe's population has Celestial birth as one of the arguments in favour of his own agenda, even though probably that isn't the case in every planet (Xandar and Hala may probably have more population than Earth, unless that's just because, for some reason, no Celestial was planted there or it may have died during gestation or before birth, or something like that).

EDIT: This gives me a thought regarding how does that fit Agents of SHIELD S5 Earth's destruction. Could perhaps the gravitonium be somewhere linked to Tiamut? Like some form of amniotic sac or something? And through some form of powerful excitation caused by Talbot, it creates a shockwave across the planet that leads to a premature hatching of Tiamut, destroying Earth as a result. I mean, even if gravitonium and Tiamut are unrelated, Tiamut was definetly gestating on Earth at the time, so his status should be questioned. This actually also leads me to connect this with Titan which, funnily enough, also has some gravitational phenomena occuring across its surface, perhaps a result of a gravitonium crisis, which might be linked to the planet's destruction? I don't know if my thought proccess sparks some interest in you. It feels like there's something that could be worth linking into (doubt the movies will ever connect these dots, but whatever).

In the comics thanos is an eternal

And I was also thinking about what if the emergence is actually what destroyed the world in agents of shield but in my mind the dates didn’t line up correctly

And I know thanos is a titan so is his brother but they are also eternals

Did you notice how in the movie Eternals, the titular eternals had free will and constantly questioned their mission and purpose? And did you also notice how a good portion of the titular eternals directly opposed and sabotaged their mission and the ones behind it (the Celestials)?

No offense, but your question is rather silly given the literal plot of the film. LOL

Free will to an extent they all were following their actual mission without even knowing what it was. None of them were out there slaughtering humans for the most part besides thena and gilgamesh they were helping and being apart of humanity. When they straight up went against their mission three of them still on earth were abducted. The plot of the film is them finding out that their main mission wasn’t what they thought it was so I have absolutely no idea what you’re trying to say

They stopped one emergence to save humanity and got abducted. Thanos stopped every single one that was in the works by killing half the universe and the celestials are just like “nah you do you bro todo bien homie”?????

So your question is really, why didn't the Celestials abduct and judge Thanos?

A few possibilities:

1. Thanos only delayed their plans so it wasn't deemed important enough.

2. Since he had the Infinity Stones the Celestials may have been afraid to challenge him.

3. Marvel had no idea they'd create this story when developing Infinity War and didn't want to stifle the writers of Eternals. My guess in this case is they'll choose one of the above answers or a completely different one.

In the comics thanos and aros are like the first natural born eternals so they're technically not cosmic robots like the rest of them I think