The Prophet said that if someone does a good deed and makes someone else a partner with Allah in it, then his whole deed is for the partner. Allah hates that action as well as its doer. It has also been reported from Imam Ja'far Sadiq that if someone performs an action for fear of Allah, or for the recompense in the hereafter, and includes in it the pleasure of a human being, then the doer of that action is a polytheist. One kind of polytheism is that which relates to causation since most people base their hopes and fears on secondary causes. This is also polytheism, but it is pardonable.
Polytheism means to think that power lies intrinsically in secondary causes.
For instance, the sun nourishes many things in the world, but if one considers this power to be inherent in the sun, then this is polytheism. However, if we believe that the power of the sun is given to it by Allah, and that the sun is only a secondary means of His munificence, then this is never polytheism. It is rather a form of worship since to pay attention to the signs of Allah is a prelude to attending to Allah. A reference has been made in the verses of the Holy Qur'an to the fact that we should ponder the signs of Allah since this leads the attention toward Allah. I admit that all you have said is correct, but if you would just take the trouble to think for a moment, you will agree that to rely on the imams is polytheism.