For me, there is only one real problem with this game. Whether it is a setting for this particular world or something related to InnoGames' business model is not my concern. What is my concern is this: who can attack me. I don't care if I am allowed to attack someone with a larger village than I have or not. What bothers me is that someone can attack me and wipe out my troops because they either spent money to advance more quickly or started much earlier and therefore have used more time. If I have 100 troops in my village and someone attacks with 2000, there is absolutely no chance I can defend my village, REGARDLESS OF WHAT KIND OF TROOPS ARE USED (Except scouts, obviously)!! Likewise someone with a 1700 point village to my 350 point village is going to have a much better chance of winning even with troop parity.
I see at least 3 ways to fix this. First, make a world with 3 or 4 times the Barbarian villages and no PvP. This eliminates the veteran players from destroying the new players as the world gets full, but comes with some serious extra work for the Barb villages, since they now need to attack the players. Secondly, prevent a player from attacking a village with fewer points and/or fewer total troops. Thus, if I have 350 points and 2000 troops, whether they are at home or somewhere else, I can only be attacked by someone with no more than 350 points or fewer than 2000 total troops. There is a balance somewhere in this, of course, and it could be a 10000 point village attacking with 50 total troops or something like that. Both of these methods come with their own problems, of course, and they are not the way I see as the best method to fix my original concern.
The best way in my opinion to fix the issue of those who spend lots of real money always winning everything is this. First, a player can always attack up and can always attack a Barbarian village. And a player can attack down provided there are some balancing effects. I'm going to use some D&D-style terminology to explain my idea. A player may only attack another player's village with no penalty if that village's points are within 90% of the attacking villages' total points. This allows coordinated attacks so that several smaller villages (or tribes) can reasonably defeat a single larger village, but reduces the likelihood of the 1700 vs. 350 point attack I described earlier. If the difference is greater than 10%, the attacker takes a penalty (or the defender receives a bonus) of 1d10 * 10% for each additional 10% difference. Here is an example: Attacker is from a 1000 point village, the defender is a 500 point village. This is a difference of 50%, so there are 4 "die rolls" ((90 - 50) / 10) to determine the penalty. The minimum penalty would therefore be 40% (4 rolls of 1 each, multiplied by 10%), and the maximum calculated penalty would be 400%, although a cap of 90% penalty seems reasonable to me. There should also be a comparison to number of troops, with a similar calculation based on actual attacking troops vs. total number of defending troops, regardless of their location or type. I think the current attack/defense calculation is reasonable once the battle is joined, but a 2000 troop vs. 100 troop battle is simply too unfair. However, if I decide to leave my village uncovered, it's my own fault that I lost, not the attacker's. So, for example, if I have 1800 total troops who are all out scavenging (or attacking someone else), a person (or group) attacking me takes no penalty if the total troops actually used in the attack is 2000 or fewer, regardless of how many troops that person (or group) has in total. Note that this calculation should not include scouts, since those can do no direct damage.
Ultimately, my point is that until there is something that forces reasonable parity among villages involved in battles, there is no reason to make this game free-to-play, pay-to-win. It might as well be pay to play, since the only people who can possibly enjoy themselves are those who spend large amounts of real money. This is why I quit playing 8 years ago, and why I will probably quit playing in the near future. I don't mind losing sometimes, but I should be able to win at least once in a while if you are going to call this a free-to-play game.