Well that's the thing. You go to a classic car show and think, wow, they really built things to last back then, here are all of these examples. But you can't have examples showing what didn't make it, because, well, those things didn't make it. So even though the latter group might account for 99% of all cars from that era, 100% of the examples you have come from the 1% that lasted. That's survival bias. For example, this place where I do some work still uses older (90's) computers because, even though they're 20 years old, they still get the job done, and only have one job to do, so why upgrade needlessly to a different and unfamiliar system? Seeing those 90's computers and thinking, about how long they have lasted is not evidence that computers in the 90's were built to last longer, it's just evidence that that computer has lasted. And with both of those examples, care and maintenance are part of that equation.

But let's take something less complicated. Calculators. You might pull open a drawer to find, stuffed in the back behind some old papers, a calculator that you haven't used for decades. And it might still work. You might then think about how cellphones these days need to be replaced every two years, and then conclude that technology today isn't built to last like it was back then. But that's apples and oranges. A calculator today will probably last much longer, if only for the marginal improvements in batteries and small PV components etc. Likewise, I'm sure an oscilloscope purchased today would enjoy a long lifetime of use as well.

Yes, consumer electronics, by nature of them being much more complicated and constantly improving, and being used daily, and brought around in pockets, and on airplanes, and trains, and in the rain, everywhere really, will probably be replaced more often than a laboratory electronic. However, with enough maintenance and care, there's no reason that a cellphone made today couldn't still be running in 20 years, just like a classic car or old computer.