Well, I'd be hard-pressed to call any Maiden song from the 80s filler, but I happen to like their style. Anyway, "Die With Your Boots On" gets a lot of criticism for having stupid lyrics. Let's analyze:
"another prophet of disaster . . . predicting war for millions, in the hope that one occurs ... terror, death, destruction pour from the eastern sands". Well, 20 years later there was a leader in America that was always talking up the terrorist threat from the desert lands of the middle-east. This allowed him to invade Iraq on false grounds, gave him power to override many constitutional rights, and send many people to "die with their boots on" in wars in those eastern sands.
There was a lot of terrorist threat from the middle-east in the 80s, too, and politicians have always used fear and war as ways to manipulate the masses.
So, these lyrics seem pretty pertinent to pretty major world events, in my mind!
"Sun & Steel" is about "the Book Of Five Rings" - a 17th century book of military philosophy written by a respected Samurai.
What you consider stupid lyrics obviously is your opinion, but I always considered Bruce Dickinson's lyrics to be some of the most intelligent and insightful in rock or metal. Even Steve Harris's story-telling songs give great imagery to the epic, energetic music. Surely this is much better than songs about groupies, fast cars, and rockin' (or Halford's thinly-disguised lyrics about gay escapades - and, I mean I like Judas Priest, but I'd say Iron Maiden's quite a step better), or the whiny poor-me Grunge/alternative lyrics that came a decade later?