A lot of people debate why the game used to be more interesting. It's no doubt true, personally the time before and around the first Great War was my favorite part of this game, and I know many others will agree with me.
There's a few major reasons why I think this game isn't as fun as it used to be...
Back in the day, you knew who the big alliances were, and what side they were on. They were all huge players on the political field and had very active memberships. You could probably count the major alliances on two hands:
NPO, GATO, LUE, NAAC, GGA, Legion, ODN, NpO, and some major mid-sized alliances.
More players, less alliances. There was always a "cold war" feeling in the air. When one of those big alliances did something, it somehow affected the others, so there was just so much more involvement. Nowadays, an action has to directly involve your alliance for it to be of any concern to you. With so few major players, the political scene was a lot easier and more entertaining to follow. Now there's over 10 trillion alliances and the treaty web, blocs, and so forth just make things so much harder to keep up with for a person who can only devote a little time of their day to this game, and honestly just make a joke out of the politics side of the game, which is what attracted so many people in the first place
This small number of alliances also created "the good cause," I guess. Your single alliance could make all the difference, meaning you could make all the difference, and that's pretty nifty