I wouldn't be too harsh about Joel Schumacher involvement in a downfall of the Batman movie series. It actually started with Tim Burton who, after success of the first Batman movie, was given a freedom to do anything he wanted in the sequel without anyone watching him. Thus we end up with a very divisive movie that many called too dark and bizarre, which also kinda dissapointed the higher ups in Hollywood with it's income. So they decided to replace Burton with a Schumacher and forced him to make much brighter, more family friendly and marketable film. Joel himself was a Batman fan and he loved Burton's adaptations, so he wanted to stay consistent with his style, before the producers said no. That's why both Batman Forever and Batman and Robin ended up being nothing more then just a mere products, because this is exactly what producers wanted, just something to sell. Schumacher clearly didn't like that, but he had to follow orders to stay in business.
