I am gonna have to keep this short to keep my promise :)

"Poser 5 should have been written to accept as many characters on stage as Poser 4 can, including on Windows 98, since very many people satill have Windows 98. Many people can't afford to keep on buying more Windowses or more computers."

Poser 5 can hold as many characters as Poser 4, you just need a fairly recent computer to do so. There is no way to keep advancing software and supporting Win98. It just can't be done. Win98 lacks basic, fundamental features needed by memory intensive programs like moderately advanced 3D systems under heavy load. The amount of extra code needed to try would be huge, and the effort would be doomed to fail.

"Also, the CR2 language to handle Poser 5 nodes should have been made much more compact. The size of a Poser 5 uncompressed .CR2 for an ordinary model such as the Businessman, is unbelievable."

It's the trade off for an open, easily modified and human readable format. The solution was to allow users to compress those files, and it is a good compromise.

It is unfortunate that many people cannot afford to upgrade their machines, and they will simply have accept that at some point that means they will not be able to run the current software.