Bulgie above, nails it. Mountain bike applications back then~ definitely was hard on chains, rapid wear on small aluminum chainring, rear derailleurs tension spring sometimes could be fine tuned tweaked to help avoid dreaded chain suck. Long crank arms (175) were the thing as well. Consider the extra leverage equates to added stresses. The worst though is a chain snapping while standing and pedaling.

I was using Ritchey Logic cranks yet I forget whom actually made them, might've been Sugino. Little ally ring would quickly wear out and same for the chain. Wanted to maintain lightness yet avoided steel ring so then splurged for SRP supplied titanium rings.

These days we have more options and improved components to tackle these super ratio's, capacity and wrap. Lots of experimenting for the older stuff, hacks and adapt with new little parts. Drill and reclock for internal spring tension, adapt to longer aftermarket arms, various tooth count jockey pulleys, extended derailleur mounts etc..

But even if you got all the above dialed in for some vintage touring rig, think about the crank Q- factor plus torsional flexing of a weighted down steel frame. I've had some perfectly operating mountain goat climbing bikes on the workstand but definitely didn't act the same in real world conditions.