Looking at the older bikes, they usually came in entry level, mid level, and high end. Sounds like you have been riding entry level. These bikes usually come equipped with stem shifters, safety brake levers, and clamp-on rear derailleurs. Entry level bikes also come with steel wheels and steel cranks.
Look for bikes in the mid range. They can be a lot of fun, and should come with down-tube shifters, bolt-on rear derailleur, and aluminum components like rims, cranks, handlebar, stem, and seat post. In your price range, they should be ready to ride!