What I like about Symbiosis is that it actually treats the subject matter with a good degree of maturity. It doesn't simply color in the lines with "good guys and bad guys", but instead explores the whys and wherefores of how supply and demand works. The episode is also an effective analogy of, say, commercialisation. The consumers don't know that they 'need' something until the suppliers convince them that they just can't live without it.
The second half of TNG's first season really did see a marked improvement in the quality of the stories being told.