The statement does not seem to make a lot of sense, and I do not see how this relates specifically to history over science / technology subreddits, because as far as history goes, we still have not reached a "maxed peak" on "technology".

Also, I don't see how technology reaching a "maxed peak" would cause a "downfall". I assume "maxed peak" means "maximum efficiency", in which case begs the question what mysterious outside force would cause the downfall.

I don't mean to be rude, but the statement your sister made is just... not stupid, but misinformed and poorly constructed.