The idea of progress (or decline) is often avoided because it means judging other cultures both in the past and the present. But we cannot help but wonder if things have been getting better (or worse) over the course of time. The key problem for assessing progress it to have a principle of evaluation or a standard that applies through history – it cannot just be a standard or principle that is fashionable now but that was irrelevant in the past. (We cannot be chronocentric.) A second problem is to discern whether there has been overall progress in all areas of life, and which areas have seen more progress, and which less. A third challenge is to consider and compare progress in different areas of the world. A fourth issue is to figure out if progress has been gradual or abrupt, bumpy or smooth.
The idea of progress was classically contested by the idea of decline: that Eden, the Golden Age was in the past. Rousseau thought the simplicity of the noble savage gave way to the decline of life in civilization.
These are hard problems; but I think that there is a principle of evaluation that allows us to say coherent things about progress: it is human nature. So, one of the main candidates for progress is science. Why? Because it has made a major improvement to our natural desire for understanding.
There is also a way of combining the idea of a Golden Age with the idea of progress. It is that progress has been U-shaped, bringing initially declines on many indices, before recently bringing improvements.