I have played v5 for more than 2 years and I want to say that v6 is much better but:
1. I feel like I will never get to elite units:Centralization problems-I think you made the time of building and resources needed a little bit too expensive c9,c10 and c11 are almost impossible to make without diamonds before the era ends. I think you should rethink this.
2. Army costs while at home or mission:Because now the centralizations are so hard to make it's very hard to have a good army. Compared to v5 where you could make 10-15 centralizations that would grant you a lot of sustain for your army here, at 2.5M population you can barely sustain 100k heavy units. You force us to make 1 of 2 choices:
a. Build a lot of army and attack everyone to grow (poor economy)
b. Build economically and have almost no army to defend. (poor defense)
You can't build both and grow fast enough to keep up with top players. And sincerely it's much better to grow economically at the moment then military and this part is not fun. I should be able to do both. (top players build economically and use diamonds on caskets to build army)
3. Trading routes are waaaaaay to expensive for their income. The stone you must invest for 3k gold income is crazy, i mean come on.. the trade routes purpose is to get more gold to maintain your army.. but at the moment trading routes aren't worth making because it uses tons of stone, you should really nerf the costs of trading routes so it will serve their purpose.
4. Defense facilities (forts, moats etc.)USELESS! f7, f8 and f9 are only build for their economical bonuses and to garrison our armies. They should be a lot more stronger to serve their DEFENSIVE purpose.
I think I overdid it a bit, but since I got few minutes of free time at work
why not share my point of view