Is that true or does it just seem that way?
Cars today are pretty reliable. Random other stuff seems pretty decent as long as you don't buy the absolute cheapest stuff around. I'm working on a solid wood desk with no nails or screws (it's called a "puzzle" desk because it fits together in a stable configuration without any connectors). I'm looking at a backpack, which I assume is nylon, and it seems pretty tough and has lasted through a few adventures. I'm looking at my metal-framed bookcase, which has fake-wood shelves but it still seems pretty sturdy.
There are certainly some things that seem worse. Furniture is probably worse overall, but that's because good wood is so much more scarce now. If you buy metal/glass furniture than it's fine. There are also some worrisome practices that are pretty widespread, like using plastic-threaded screw holes rather than metal; or just using really cheap metal that can be stripped or cross-threaded easily.
On balance, where are we? I have a feeling that we're basically better off. We remember the old stuff that lasts, and forget about the stuff that breaks (unless it's still celebrated/historical, like the Liberty Bell).