I can find the modern era annoying, since the large cities, radar towers, civil defences and mech inf just make conquest too impossible, even with moden aurmor. I win before ICBMs and all that lot.
I remeber a time when I just couldn't attack unless I had tanks, I wouldn't fight in the ancient or middle ages, or early industrial. When I changed, my whole skill level wen up. Have you ever changed your strategy, and found you can play like two levels higher? Interesting