Yeah the keepers are really bad. Sort of ruins the whole experience for me as the diving animations take all the joy away from scoring. The actual animations bug me more than the mistakes they make.
The main problem stems from the ball & nets imo. If you look when you're playing, the ball is slightly too small. The nets also look slightly too big for the keeper. In reality, they probably aren't, and it's more to do with the depth of the net (or lack of) that actually makes them look so high and wide. So small ball, big nets, keeper with poor animations/poor AI generally means scoring won't be very satisfying.
The keepers just don't command the nets like a proper keeper does. It's like sticking one of your mates in net, and he doesn't really play football, let alone know how to be a good keeper.
The keeper animations on pes6 were pretty good, and the nets were box like, and the ball seems bigger to me.