I have tried 1v1 already and Mongols really became very weak due to lose age 2 knight.
Red is Mongol and I am Rus
From the figure we can see, I just spam knight and don’t care about his Mangudai because they are too low attack. Mongols don’t have age 2 knight now what he can do is only Mangudai hit and run and build outpost. Because I have age 2 knight and Mongols don’t have, what he can do is only stay near TC for the whole game. Seems now Rus and French is aggressive civ and Mongol is defensive when facing these two civs.
In the middle of game I just build some outpost near his base and his Mangudai can’t stop me because they need hit and run, then battle situation became even worse to him because he can’t leave his base anymore due to my outpost. He also try to train some pikes but this is useless because knight is so powerful and I also start to train some archer to fight back his Mangudai and pikes. When I hit age 3, I just start to build castle to force his army fight.
Finally Mongols become completely not like Mongols style, he need to defend knight and build outpost to turtle and train some pikes to defend my knight.
Mongol is designed as cavalry aggressive civ but now it totally opposite.
IMO, Mangudai hit run is annoying but this is not unsolvable and not related to age2 knight.
I still consider Mongol should have back their age 2 knight, or other civs shouldn’t have it.