If an invention is countable (e.g computers) then you can choose to say either
"Computers were invented..." or "The computer was invented...".
If an invention is uncountable (e.g. gunpowder) then the definite article is not usually used.
"Gunpowder was invented in China;"
"Morphine is poisonous":
"Sugar is sweet";
"Paper is useful".
When uncountable inventions are listed with the definite article - the paper, the gunpowder, the morphine ... - this is usually because the simple uncountable noun has been qualified (either explicitly or elliptically) and made into a countable compound noun -
the paper-we-are-using... ;
the gunpowder-made-in-England... ;
the sugar-on-the-shelf... ;
the music-we-are-talking-about ;
the morphine-in-the-shop... .
This post is helpful https://english.stackexchange.com/a/198867/103961