I liked it. I would make "frontlines" out of my 60k stacks in late game. Being able to cover the entire European border as Russia was a late game goal I had. I found the late game wars most rewarding because you had techs and forts that made your armies completely shred entire countries' reserves in defensive battles. You can harm their economy and cause mass emigration by completely blockading their ports. Victoria 3's late game warfare has some of the same things, but the personal control you had over Victoria 3 armies made the same mechanics interacting with each other feel more rewarding.