Simple ad hominem.
I give you that one. I am still sceptical though. Please forgive me.
You were too busy cherry-picking to notice "sources of nutrition" and "human medicinal agents".
Oh I did notice that. I just cant see anything in there that tells me in a believable fashion that these things actually cure something.
I do like mushrooms for food. We go picking them here every summer.
It is also true that some fungi, under some circumstances can produce antibiotics. I do however doubt that these people understand and know that. Even if they by accident figured out that some fungi can produce antibiotics (and we dont even know that the ones they are using do), they have no way of knowing what illness to use them against.
It is ridiculous to assume they do.
How would they know what a gram positive, or a gram negative bacteria is? They dont even know what bacteria are. They do seem to know about black magic though.
Now even if for some reason, they knew all that and made it work, then their fungi would only cure some illnesses. They would still be powerless against most of the others.
That aside I just fail to take anything seriously ( and you can pick me apart for that, I dont care) that is mentioned in one sentence with black- and hunting- magic. It clearly shows that there is absolutely no understanding there whatsoever.
Find your nearest architect and try that on them...
Try what on them? Anyone with some brains will tell you that building a cathedral is much harder than piling up a bunch of rocks in the most self stabalizing shape possible.
There is nothing mythical about the pyramids. They were an awesome achievement for their time, but they were overtaken even in the antics. The Pantheon in Rome e.g. is smaller, but much more impressive as an achievement.
Still it does not matter, you are assuming that HG- cultures know things that noone else knew after the middle ages. Something that "got lost". I dont know how you get to this assumption. It does not make sense.
There was not some single event that deleted knowledge. People were always sick and people always tried to cure the sicknesses. It took understanding, knowledge and modern tools to finaly cure as many as we can cure today.