It's not helpful to scold people for being upset about this. They have a right to be upset. But I agree that, going forward, the right course is to just switch software and/or platforms completely.
The old iWork is effectively dead. As the OS continues to advance, the old iWork apps will crumble and fall into disrepair, so it's not a realistic suggestion that people keep using them except maybe short term as they seek out replacements. There is a handful of excellent and fully featured word processors for the Mac, but presentation and spreadsheet software is a different story. Apple is ceding the ground for business users to Microsoft. It's possible that Apple intends to extend and develop the new iWork so that it will eventually be able to compete with Office, but I don't think so. People believed this eight years ago when iWork was first introduced, and in that time Apple didn't put much development effort into it. Bugs went unfixed for years, and Apple's focus turned more and more towards consumer electronics devices such as iPods, Phones, and Pads.
I myself have never used iWork for much. I was excited about Pages when it was first announced, and used to have great fun just playing with Keynote, but the software always felt awkward to me, as if it didn't really know what it wanted to be, or why it existed. I would say that with this new version of iWork, Apple has at the very least finally decided what it wants iWork to be: a proof-of-concept for their cloud services with just enough features to satisfy elementary school students.
I wish that one of those guys who went on stage on Tuesday to present the new iWork had had the balls to admit that this wasn't an upgrade.