The subunits of virtually all organic molecules are joined by
condensation reactions and can be broken apart by hydrolysis
reactions.  Why, then, does your digestive system produce separate
enzymes to digest proteins, fats, and carbohydrates?in fact, several
of each type?

kinetics.

the reason that RNA produces enzymes (A Protein) is because Enzymes
speed up chemical reactions (Faster than hydrolysis).  If it werent
for these faster reactions, the human body could not absorb enough
nutrients and would cease to exist.  The reason different enzymes are
produced is because each certain substrate has a certain shape on its
active site.  The enzyme produced by your body matches the indent of
that shape so they fit like a lock and key.  Most Enzymes only have
one substraight that it can break down.

It is just not true that virtually all subunits on organic structures
can be broken apart by hydrolysis. There are some links such as amide
and ester that are hydrolysed fairly easily but there are also
functional groups that are not. The conditions required for hydrolysis
are often too extreme for the inside of  the body. It's true that the
stomach contains strong acid but at the temperature of the body this
would result in only very slow hydrolysis in certain cases. Enzymes
are extremely efficient as they have evolved (or rather the body has
evolved to produce them) to act stereospecifically at certain sites
adn consequently the reactions are very fast.