One of the biggest disadvantages of a hydroponic growing medium is the fact that you have to monitor it constantly and ensure that the weather conditions do not affect the temperature, pH and EC values, water levels, etc. And even if something changes, you have to recognize it quickly and get it back to normal so that your plant can continue to develop properly. Also, many hydroponic systems require pumps and automatic setups, which may consume a lot of energy, resulting in a large electricity bill at the end of the month.  (Of course, you can move your hydroponic system outdoors and use solar energy to save money.)  Finally, certain setups are quite costly (for instance, aeroponics), but you can always try and find cheaper methods (e.g. the Kratky method).