I hear you about those things being outdated quickly. I bought a Wallstreet Powerbook G3 back in '99 or so because it was a cool RISC laptop AND it was promised to run this amazing upcoming UNIX-based Mac OS X. When OS X came out, of course it ran...but it was an absolute dog on these machines. IIRC Apple never bothered to write optimized OS X video card drivers for these "old" machines, they just charged forward with the new stuff. The experience was definitely enough for me to swear off buying new Apple products for at least a decade (although OS X did eventually win me back).
My understanding is that these old systems were slow because the window system was a compositing window system, and old hardware doesn’t keep up well with it. Using a compositing window manager has a lot of advantages, though, which is why most modern window managers work that way.
Windows Vista also introduced a compositing window manager IIRC, and it was also horribly slow on old systems.
The Wallstreet was weird for another reason: it was an Old World ROM. You (typically) had to boot at least partially into Classic before chaining into OS X or Linux. I seem to recall using XPostFacto to get 10.3 installed on it, which might cause been a bit better than the official max of 10.2?
