Ved Prakash at #653357, the SIT to inquire the 1984 Sikh Riot cases was formed by the Hon'ble Supreme Court and not as you asserted.
Coming to the thread, while I agree that 34 years is too long a time for finalizing a case, I would like to remind you that we must be aware of the vastness and complex nature of this particular case before concluding that our judicial system is slow.
To make a general statement, though I am not saying that our system is very fast, we need to understand that the Courts can arrive at a final decision only once proper and sufficient evidence (including witnesses, documents, materials etc) is brought before it. And even after that, a court can always ask for further evidence to be adduced if it is in doubt. The delay in such cases may be even more. Judges do not sit on the evidence brought before them; they have to analyze the same from different angles and perspectives keeping different laws in mind and come to a conclusion only once they are fully convinced. A judgment is not just a report which can be corrected or rewritten, it is a final piece of conclusion on which the life or property of a person or a group of persons may be involved. They cannot hurry up in such matters. So, the Courts do take some time to arrive at a final judgment but that is not due to any other reason. Shortage of judicial officers or number of courts etc may be reasons too but they are secondary. The Apex Court in consultation with the High Courts can decide on cases that they have to hear on priority and the responsibilities at the lower levels can be chartered accordingly. These are only some of the procedural aspects that I have tried to bring to your notice; there are many other factors about which we, as laymen, are not aware.
"It is impossible for a man to learn what he thinks he already knows."- Epictetus