If you would always be matched against the same or nearly the same numbered alliances - you would stack up fiefdoms cause strong 31 people alliance would always win weak ones and there is no telling - would be there another strong one alliance with same number of people or not. Then, one day, you would level up your alliance to level 55, obtain 60 people and be with 100 fiefdoms, while all others are struggling to even get to 80. So, it would become common practice to stay at 10-15 members, collect fiefdoms and then level up your alliance. More than that - right now, only new fiefdoms come from those new and low membered alliances. If they stop to match by fiefdom count - alliances at the top would simply dry weaker ones out to 3 fiefdoms and be happy about it.
Doesn’t matter how frustrated you are about this matchmaking - it works. In a perfect world where 100 millions of people play this game and there are really ALOT of alliances - you probably would always be matched with nearly the same numbered alliances. But we have just about 350 000 of players, that’s why even medium alliances are numbered. If you want a shot at winning more - level up your alliance to 60 members and try hard recruiting. Otherwise - you would always be a food for higher alliances, in a system like we have in RR2 - it’s the only decent way for AW to work.