Has the development of new cinder block designs 'stagnated' because nobody has designed a new cinder block for probably a century? No, the existing design is fine and doesn't need replacement.
That's a very interesting analogy, since I'm currently in a Japanese hotel overlooking a construction site.
Rather than the typical cinder blocks, the bottom two floors are being built from large reinforced concrete slabs, about 1 meter by 3 meters, which interlock and periodically have apparently-plastic pieces. It definitely has increased the speed of construction over laying cinder blocks, and I suspect the slabs and plastic provide some means of safety in an earthquake.
Elsewhere on the technological spectrum, several years ago I volunteered in Africa, where buildings were built with more traditional cinder blocks. The blocks, though, were formed with poor-quality cement, and crumbled when put under load. In America in the 1980s, I was involved in a remodeling project that had to replace some 50-year-old blocks because they were falling apart. Modern blocks (30 years ago) have much more consistent quality, because manufacturers can now chemically test the quality of cement before using it.
In short, construction techniques and technology have indeed improved in the last century. Not even the traditional block dimensions are "fine" for all cases, as I see across the street, though in other areas compatibility is necessary. The requirements have changed, but you seem blissfully unaware. Fortunately, your ignorance of technological progress does not negate its existence.