It is a surprise to me that this subject is not pursued more rigorously. It is highly relevant today. And yet almost no one has a clear idea of what is involves.
My basic impression is that the term is used sometimes to disparage something people do not like. But in fact I think it has to do with Numinous reality. And I do not think that any manifestation of Numinous reality besides just the One and only creator is idolatry. I mean we do have the idea of holiness in a sefer Torah and the like.
But i am only at the beginning of this subject so i cant say a lot. My impression is that we can understand what idolatry is when we look at the Rambam's approach to a mediator. A mediator is something one worships in order to come closer to God or to receive something from God. So now we can understand what a god is even when they are not mediators. They are beings that one worships in order to get closer to in spirit [numinous reality] or to receive something from.
When i was discussing this with a hasid at the tziun of rebbi nachman he asked about Zionism. I explained that Zionism is not idolatry because it lacks this numinous aspect. nor are people worshiping it.In other words idolatry does seem to have definite parameters and it is not a term that can be thrown around at will. But it does seem to be something that is very easy to transgress and get involved in.
The Satmer Rav thought Zionism is idolatry but his view is hard to defend. It seems like he was using the word idolatry a rhetorical device,