There is a concept of yeridas hadoros - a relentless decline in the generations: physically, mentally and spiritually.
Physically mentally and spiritually? What do you mean by that? And when you explain what you meant by that, can you then tell us, did you make that up? Come on now. Those who explain "yeridas hadoros" do not claim that science goes backward and that current man knows less about the physical world and its inner workings than the iron age man did. Nor that Iron age or stone age never took place. Don't desecrate Torah, please. (I'm sure you will now quote a 20th century reactionary anti-science fundamentalist who wrote screed against common knowledge, common sense, and truth, in the guise of "Torah" and try to pass that off as if it is ancient Judaic outlook or in any way connected to our mesorah. Please refrain from this. The 20th century reactionary innovations are not the same as ancient tradition. If you have a real source, bring it. Don't bring polemics).
Let's start with something very simple. By the time of the baalei Tosafoth (c 1100-1200), some of the medical prescriptions in Talmud were already outdated due to improved knowledge in those areas. So the baalei Tosafoth recommended not to follow those medical advices from the Talmud, that they do not apply to us. Does this make sense to you that medical practice got worse? If it really did get worse, then we should be following the Talmudic medical advice because we would have preserved the "better" medical knowledge of earlier man and could employ that amidst our current "fallen" state with regards to medical science. Addarabba. The opposite is the case. Medicine improved, and the old methods preserved in Talmud from earlier, less scientifically knowledgable man were pushed aside.
The rabbis say that the invention of the printing press was sent from Above only in the 15th c, because so many cartloads of hand-written Talmuds had been burnt, that knowledge of the Toral sh'baal Peh was literally in danger of going lost,
Nonsense. There was no such danger. Do you realize how many extant manuscripts there were at that time? In Yemen alone, the Yemenites preserved handwritten manuscripts of not only the Talmud and Torah but also works of Rambam, midrashim and others, straight through to the 21st century! In all that time they never knew a printing press existed, nor did they care to find out about it or use it. They were able to preserve Torah she baal peh the old-fashioned way. And this is only one example.
At times in history in some places gentile hordes burnt talmud, but we never "ran out of copies." And that did NOT happen in every place. They were not burned in every major place that Jews lived.
and men's memories were becoming fallible.
Completely false. Rav David HaLivni could recite Shas by heart in the concentration camps. The Rogatchover Rebbe - would you say his memory was "fallible" ? Please. How about Rav Ovadia Yosef of today. He has a "fallible memory" ? Rav Chaim Kanievsky? Come on. Printed or handwritten, they could remember things then and people can remember things now. There was not a danger that all of oral torah (already written down) would be lost. What you are saying is a fable.
Hashem in His mercy bestows inventions, and the inspiration to invent them, to support men's declining spiritual, physical and mental abilities, only when they are needed. If they are not needed according to His Plan, the inspiration won't come, or the invention won't succeed.
You are again contradicting yourself. Please operate within the realm of logic. If man NEEDS a new invention to "come down from above" to support his spiritual and otherwise decline, that just proves that the new invention is an IMPROVEMENT over man's previous technological state. (You are saying first he's spiritually high in 1980, doesn't need much technological aid, then he falls a bit spiritually by 1990 and needs a little "boost" to counteract that or compensate for it, so Hashem drops a wireless device on us, or what have you). You are implicitly agreeing to what I said that scientific achievement and discovery INCREASES as time moves forward.
If you want to say that that scientific improvement is necessary to support and bolster mankind as it spirals into moral decay and/or spiritual decline over time, that's fine. You still admit that basic fundamental truth that scientific improvement occurs with time. To deny this is to deny reality, which is a desecration of the Torah. And look, you can't really deny it because faced with sufficient challenge, your words have admitted to my premises. Now open your eyes and acknowledge that you have done so.