[Thumper]

Monoshock and swingarm design alone has improved immensely, but many chinese bikes still have the box steel design (like my Storm), so yes and no there. Hollow cast steel alloy swingarms with SOLID axel slots welded to them are available on some (Templar, KPX, for instance). These are stronger. Some Chinese bikes still have standard forks, but others like Hawk DLX, Bashan Storm, Brozz, Recon have inverted forks. Templars too. But bearing fit, slop is variable. So it is a mixed bag on suspension.

The engines we buy today are based on much more modern 4 strokes, and they are fundamentally better engineered/cloned, BUT we see bad Zongshen and Lifan engines periodically here, so QC is NOT necessarily better than the 70s. In fact, I would say QC is definitely still an issue.

I had a mid-seventies Suzuki TS250 2 stroke. It was more powerful than the 4 stroke 250s we see today, and much more dependable statistically. But not so much torque at low rpm that a 249cc ZS172 can make, which is crucial for off road stuff. It was still amazing fun. The suspension was meh, and the bike was heavy and not so stiff back then (Yamaha seemed to make more progrees here)..

I would say mixed bag, but when you factor in price, the bikes we see today from China are head and shoulders above those 70s Japanese bikes in many ways. But QC on parts and build quality are still major issues. You have to go over everything and be ready for anything.