What is idolatry? Bowing, burning, bringing close, slaughter and service according to its way.[note 1] And it helps to have a clear idea of what idolatry is so that one is not tempted to use it as a general catch all phrase for whatever one disapproves of.

[So when I say that the religious world is doing idolatry, I am not saying going to Uman to pray in the merit of Rav Nahman is any kind of problem. Rather the issue is attitude. And even if one can not be legally guilty, it is helpful to have an idea of what the actual essence of the issue is. As the Gra said to judge any action one needs both to know the law and also the situation.

[note 1] These are the four services done in the Temple. If done for an idol, the one doing them is guilty of idolatry. Bowing is understood. burning is like in the Temple when one brings  a burnt offering. If that same act is done for an idol, it is idolatry. The rest are understood. The last one means this: sometimes an idol has a certain kind of service that is unique for that idol. So that is also idolatry if one does it. Now what is an idol? Anything. It does not need to be an object. But any object will do. So in the religious world when worship is done towards dead people, that constitutes idolatry.]