I have my personal opinion about it.

If we start to count the indicators we are using every day it will be all the indicators posted here. We are too different people (traders) to use the same indicators or trading systems. You must find something which will be yours according to your character, experience, desire etc.

If some indicator is useless for somebody it does not mean anything: this indicator may be useless for this particular person only according to his personal opinion and personal experience and other people may use it with some success. I have many examples when some people refused to use some indicators or systems and the other people are using it. And it does not mean anything, just a personal opinion. And we have as many opinions as the traders. No one can tell to anybody: "use this indicator or use that one!" Because nobody will believe in the decision which the other person did concerning this subject. Why? Because of real money you are trading with.
If the people want to explain why some indicators or systems are good (or not good) for them they may do it in Discussion area. But it will be their personal opinion. If you understand yourself as a trader you will have your own personal opinion.

How to form the personal opinion? To listen to somebody's advice/opinion trying to analyze:
why (he said like this)?
when (he changed his opinion last time)?
what (is his experience)?
what (is his income coming from)?
where (does he work)?
which (group of the people he is connected with)?
what (he or this group of people wants to get from this forum)?
what (is the other group of the people with opposite opinion)?
etc