I’ve played AoE3 (AD & WC) for a couple of months with my group of friends way back in 2009, then I played AoE3:DE a bit during pandemic, but I had to leave it, since the guys prefer playing AoE2:DE; however, I have to Say it: AoE3:DE is a better game than AoE4, it is more balanced, there are more alternatives for strategies, civilizations feel more unique and even have better aestetic.
The only thing that really seems amazing about AoE4 (Compared to the rest of AoE games) is that units can walk over walls, allowing you to create actual fortress and providing actual usage to the siege tower, and that mangudais can shoot while running. The ambush mechanic is pretty neat, too.
From a competitive and balance point of view, it’s a shame that the gunpowder units can deal with almost every other unit in the game, AoE3 and AoE2 solved this in a more elegant way, keeping the rock-paper-scissors model pretty much balanced. Siege should be nerfed somehow (research time, construction, make it slower or more vulnerable)
Now, I understand that in real life gunpowder was a game changer in medieval warfare, but they started being mainstream on XVI century. Before then, they were unstable and prone to explode, their logistic was chaotic and their most common location was being used as defense on fortress or for long sieges, since the mounting and dismounting took a lot of time and manpower.
Taking that historical reference into account, it would make sense that the first gunpoders weapon in early imperial age would take ages to move and to aim, or even take damage when shooting; then you would need to invest a lot in the university to improve them, eventually unlocking the field guns that are more dynamic and reliable, but that would be late imperial.