There's lots of talk about the fact that iWork has lost a significant amount of features on the Mac. Many people attribute it to Apple being blind to the needs of pro users. I think the reason is far less condescending.
The phrase "the same file format for both Mac and iOS" is used on the pages for all three products. It was highlighted in Apple's keynote. It's important.
Without all versions of iWork using the same data format, true interoperability is impossible. In the previous versions of iWork you would lose some formatting & data when moving from Mac to iOS.
When you create multiple apps that use the same data format, it is difficult, if not impossible, to prevent data loss when editing files unless you have feature parity between versions. To make up a fictional example, imagine that Pages on the Mac could include images in a document while the iOS version could not. What happens to the complex text wrapping around an image when you edit the document on the iPad? What happens to page layout, and links, and your table of contents, if large chunks of content are missing? You'd end up with serious formatting errors at best, or data loss at worse.
The fact that iWork on the Mac has lost functionality isn't because Apple is blind to power users. It's because they're willing to make a short-term sacrifice in functionality so that they can create a foundation that is equal across the Mac, iOS, and web versions. It will take time to bring these new versions of iWork up to parity with what the Mac used to have. In the meantime all platforms have to live with the lowest common denominator.
Whether this tradeoff is the right call is up for debate. As someone who uses iWork a decent amount, it's frustrating that the first update major new release in over 4 years is a regression in functionality. But if iWork is a key piece of Apple's software platform going forward, it's easy to see that interoperability across versions is an important baseline requirement for them. I just hope that they continue heavy development of the software and iterate quickly.
Caveat: this is all hypothesis based on my experience designing cross-platform software. I could be wrong.
Update: It was pointed out to me that the new iWork for Mac is not the first update to the software in over 4 years. There were many updates to iWork 09 over the years. The first "major new release" is more accurate.