Not making assumption here, but how much do you weigh and what was the chair rated for? Actually, don't answer, just check it out. We have found that the chairs we use at my office that have plastic stress points used to be rated at 250lbs, but are now only rated for 225lbs, even after a redesign of the stress point. What we have found is that, for anyone over about 220, the charis really will fall apart much faster. I'm around 215 and I switched models because I was tearing up the 225 rated models. We actually looked for heavier duty chairs for our big guys, and it has made a difference. More metal parts and even sturdier hydraulics. They cost a little more, but it's less than $100 per chair. I think we looked for Big and Tall models to find the ones with higher weight ratings. Even if you aren't over 225lbs, you may like the sturdier construction.
As for why they are all made more poorly...well, labor and materials are more expensive thanks to inflation mostly. That, and many people don't WANT their stuff to last forever. They want a new model every few years. C'est la vie.