That is true but there are a lot of progressive elements in BNW and even some acoustic stuff kind of like a second addition of Seventh Son
This is why I can't get into a lot of metal that tries to emulate old bands, such as a lot of the Sabbath rip offs that have stated to pop up lately. Part of what makes Iron Maiden awesome is that they were so progressive right from the start. Bands trying to sound like Maiden kinda miss the point and aren't every exciting. I much prefer groups like Opeth, Metallica, or even the power metal bands like Helloween or Gamma Ray. Bands that take a Maiden influence but do something different with it. That's what it's all about.I'd argue that being "progressive" in the original sense of "pushing beyond established musical frontiers" has been part of metal from the start, and in fact is how metal got started. The conventions of "purist metal" were only established later. Metal bands which have retained a progressive spirit are more true to metal (IMO) than those which refuse to step outside any "purist" box. Thus, I assert that "progressive elements" make Maiden more metal, not less.