I not totally agree with you. I played COH3 pre-alpha version and this game looks much Better than AOE4: Waters, textures, units, terrains, all materiale seem Great and this Is a pre-alpha.
So, it’s not Relic because CoH3 uses the same engine: CoH3 looks brillantnbut very very detailed. For AOE4 It was a decision by Zach Schlappy (the Art director) and Adam Isgreen (game director). They listened all of feedbacks from the AOE Councill (few players) Who wanted only readability and the final result It was: less textures, Unrealistic Building sizes, very bad Water, Plastic weapons etc. All of these things are killing realism, imho.
World’s Edge probably Think that AOE4 Will be good After all and player Will don’t care about graphic due the gameplay and the name of this game 'Age of Empires".
AOEO have been a good example for that: It was very fun game but too cartoonish and very far from what people were waiting for. It was not a Simply marketing issue (not skirmish at launch, only Two civilizations, pay for win etc): AOEO was already dead before its Launch due the negative reactions which started with the First announcement at Gamescom 2011. The most of fans called It : Age of Farmville" and they choosed didn’t play the game for this reason.
Now, i’m seein the same negative reactions on AOE4 and this Is a very bad sign.
I think a delay to spring/Summer 2022 could help a lot: developers should redine all models and units with realistic textures in the same way they’ve done with CoH3, change water, add people to siege weapons etc.