That is assuming one buys into the fabrication of something being lost in the first place.
Before the Scientific Method was devised, one of the problems is that advancement of material knowledge had plateaued because discoveries were kept secret. Secret knowledge was lost across generations even when it was leaked to others. The leaked knowledge just took longer to be lost. So science exploited a human frailty that competes with the desire for secrecy - The desire for fame. In science credit for a discovery went to the first to publish. Once published, discoveries were no longer lost. Material knowledge left its plateau and has been advancing ever since.
When grand lodge Freemasonry was invented in 1717 the formal codification of the Scientific Method was still new. Optimism abounded that the principles that worked so well in the material realm would work as well in other realms.
Freemasonry was called a progressive moral science. I suggest that the expectation at the time was that morality in general across the world would increase through improved knowledge and the application of that knowledge. Has this happened? Certainly not at the same rate as happened in material knowledge but I do suggest we have seen progress.
Understand that complaints about moral decay since the previous generation are so universal to humanity they appear in works as ancient as the Illiad and the Odyssey. When considering moral advancement across time we need to understand that most of us have this bias to see our times as worse that before, and we need to move past that bias.
For a while the number and size of wars kept increasing but with the invention of nuclear weapons that trend stopped and reversed. The world definitely still sees wars but there size remains small. I wonder of historical demographic studies would even show that the percentage of the world covered by wars has been shrinking. With the world entering a new set of Crusades let's hope they don't last the centuries that the previous Crusades did.
More and more of the world is being covered by republics-in-fact and less and less of the world is being covered by republics-in-name-only. More and more of the world is being covered by active trade. Historically when republics-in-fact engage in active trade the chances of wars decrease.
Economic booms and busts continue about once per decade, but at the worst point at the bottom of each cycle the percentage of humanity starving ratchets down. With another couple of cycles and with globalization of trade we may even see the absolute number of people starving down down.
In western secular civilization various forms of equal treatment continue to advance, as usual over the objections of previous generations. One topic at a time. Religious attendance continues low in countries with any sort of official religion, continues high in countries with high degrees of separation of church and state.
Moral progress has been at a much slower rate than material progress, but it has been happening. Often with Masons leading the way as dictatorships give way to republics, as peace prevails after wars.
As with material progress, I am sure that moral and spiritual advances have been lost over the millennia. Calling Freemasonry a progressive moral science and keeping our service events and charities publicized helps keep new advances going.