Repetitive choruses are the achilles heel of modern Maiden (read post reunion). There were some repeat-lines-over-and-over choruses on early albums too, but they were a minority and even then, the lines each differed a little. In Deja Vu, the chorus lines are not exactly identical, the differ slightly in every second line.
On post reunion Maiden albums, they are usually exactly identical, and that's not the exception, it's the standard. Plus, the vocals often simply follow the guitar melody to make it even more repititive. In many post reunion Maiden songs, the chorus is the weakest part of the track. Different World is a perfect example. Great song, but the chorus really drags it down.
It is a development that really came to be with VXI and existed ever since.