Hi,
On a personal note, I am not so negative. Lets not forget that we are still part of an ongoing revolution. I got my first digital SLR camera around ten years ago and that camera has served my family for all those years. My dad was using it, the main reason he switched was that we wanted to standardise on batteries. Other than that the camera still works fine.
The reason cameras are short lived is development, new technology replacing older technology. This has been very obvious with sensors with significant increases in capability for each generation. More pixels, higher ISO-s and less noise.
Especially, increasing the number of pixels demonstrates lens limitations. A lens that was just adequate for 24 MP will look bad on a 42 MP camera, especially when viewed at actual pixels, but the 42 MP camera will still make better prints with the same lens than the 24 MP camera did.
Of course, if we don't print we don't need more than say 10 MP as that is what we can see on a 4K screen.
Another change is that we shoot more zooms, and good zooms are difficult to make. A good zoom may equal a good prime at some part of it's zoom range, but it is very difficult to make a zoom that is truly excellent trough it's entire focal length range.
The Sony 24-70/4 is one of those zoom lenses. Quite obviously it is not excellent, although some users find it very good. It is probably more convenient than carrying 24, 28, 35, 50 and 70 mm lenses. Sony makes some great lenses like the 35/1.4, 55/1.8 and the 90/2.8G macro. Both the 16-35/4 and the 70-200/4 seem to be pretty good lenses, it is unfortunate that Sony lacks a really good 24-70/4.
I don't really find that the AF-generation of lenses are unreliable, I have a few from around 1990, and I wouldn't rule out they are going to survive me. The main reason that those lenses see little use is that the newer lenses have features like longer zoom range, silent and fast AF and better correction of axial chromatic aberration.
Clearly, there is a lot of cost cutting going on in the industry and some new concepts may fail. When they do we need companies and dealers standing firmly behind the products.
Best regards
Erik
Of course the other big development that has totally altered the landscape of the photography market, and the way we even think of our tools, is that it has now become simply part of the massive global consumer electronics industry. This is as evident in the printing segment dominated by Seiko and Canon, as it is the camera and lens area.
It's really a throw away culture by and large. I have no emotional connection to my photography equipment anymore like I do my old view cameras and lenses, enlargers, Rolleis, and my vintage guitars. With electronics products, as with smart phones and all fashion items, one day your in and the next day you're out. It's all going to end up in the landfill before long so none of this stuff, as expensive as it is, is ever designed to last. They don't want you to keep anything more than a few years, including the art you make with it.