Well, the issues aren't really "stupid"... technology advances, so the newer version of Poser uses more sophisticated systems than older versions did. Content for older versions had to use kludges to achieve effects P8 and above now do incredibly well.

So, the problem is the older content, not your newer verson of Poser.

To fix any problems you might encounter, you'll need to:

1. familiarise yourself a bit with the material room - there's lots of threads on shaders on here. Read a lot: there's a lot to read.
2. have a read of some of the stickied threads
3. have a stickie-beak in the wiki
4. match lighting with version. Poser 8 lights are different, better, and render well, but they bear studying a bit.
5. When/if all that leaves you unenlightened, the manual comes in pdf format in the Poser 8 folder

Monterey/Mint21.x/Win10 - Blender3.x - PP11.3(cm) - Musescore3.6.2

Wir sind gewohnt, daß die Menschen verhöhnen was sie nicht verstehen
[it is clear that humans have contempt for that which they do not understand] 

Metaphor of Chooks