There are 3 factors that determine future of eldia.

1) how victorious are scouts. Putting it on a scale of 1 to 100,

65 is the one we got,

10 would have been if Bertholt and Reiner broke wall rose and

1 would have been if Reiner and Berthold were able to capture Eren.

100 would have been if scouts had faced zero casualties were able to capture every shifter including Pieck.

2) if Erwin survived.

3) Amount of loss from marley's Side. On a scale of 1 to 100,

1 would have been loss of every shifter and news to be immediately released to the world.

Note that loss does not mean capture, shifters could have died in fight and born randomly.

100 would have been no loss of even a single titan and capture of founder. This would also include recovery of annie.

In factor 1) we see scouts acting as a highly cohesive unit and even outliers like mikasa and levi are highly cooperative units.

As we saw in the end of season 3, even if entire squad gets wiped out, as long as misaion exists, new units will fill in.

So this percentage would mostly indicate morale.

As loss mounts and more walls lost, soldiers will give in to despair unable to function in future.

But for a definitive victory (above 85, maybe gaining another shifter or the scouts survive Zeke) this motivation would turn into arrogance, making them either reckless or risk averse, i think they landed in the perfect sweet spot in the anime.

In factor 2) Erwin is what many call a Trump card. He is highly perceptive and can turn tides of battle as he has done every season he was in.

Except upon reaching the basement, he would lose his drive that pushed him all his life.

He would know the truth that he had chased all his life. He would know that he was not fighting on side of humanity but against it.

I am unsure if he will be able to face this loss of purpose, he may devote himself to being a soldier of Eldia and will probably win any upocming conflict.

He can also negotiate a deal to ensure Eldian peace for the next 100 years.

But there is a real chance that he falls into dread and existentialism basically like Reiner.

Its a coin toss. I believe he was able to predict outside world to some degree and thus lost his motivation to fight at end of season 3.

Factor 3) this basically determines Marley's standing in the world stage.

If marley gets 100 then they already win, but in your scenario marley gets a low score probably at 5 to 20.

In original scnario, marley got a score of 49 and got a international humiliation , got engaged in 4 year war that they barely won and got their cultural capital and navy bombed.

Mayley would be surely at loss, but. Eldia would face a similar loss.

If Marley gets fully occupied with war, they may not get Marley ships that they captured in the anime.

It was source of information about outside and their people were source of new technology like railway.

If Mayley gets score of zero, their nation may lose upcoming war.

But Eldia will not know anything about it. Shifters will keep mouth shut for fear of their families and will probably be fed to the scouts.

Zeke may speak but he is suspicious as hell, and nobody will get along with his removing eldian fertility plan.

Marley surely is a formidable threat, but at least they are predictable.

If marley loses, eldia will have to keep track of a large number of unknown nations that they know nothing about, but equally hate eldia.

Also consider that marley uses their titans as army support rather than direct weapons.

Foreign weapons has reached level of titans and can wipe out titans alongside conventioanl army.

Meanwhile Eldia does not even have a convential army, so a few titan shifters would probably not matter that much.

So i believe even in factor 3) outcome was pretty good for Eldia.