Also, and this is off the top of my head. Perhaps the two are not imcompatible, but it seems to me that the belief in indulgences could get in the way of Orthodox theology dealing with the Uncreated Energies of God.
This is something I've never been able to understand... (energies of God). I can't even remember which church believes they are created and which believes they are uncreated.. or how that relates to God's essence.. sorry can't comment on that at all.
Fr. John Matusiak is
far better at explaining it than me. The following may help shed some light on your inquiry.

He gives an overview and then delves into energies/etc. It's long but well worth the read....
The Roman teaching re: indulgences is linked to the notion that, while one is forgiven of one's sins through repentance and the sacrament of confession, one must endure punishment for, or be "purged" of -- one's sins after death, before one can "enter heaven." Hence, according to the Roman understanding, upon death the soul must "enter" a realm/place called "purgatory" -- the root of the word is "purge" -- so that the punishment due them as a result of their sins, even those forgiven in Confession, may be "purged" and their souls may be purified in order to "enter heaven."
An "indulgence" is a "pardon" of sorts by which the "time" one must spend in purgatory is reduced. Since the souls in purgatory cannot repent, they rely on the living to participate in good works, specific prayers, and other activities that "generate" a partial or total [plenary] reduction of time in purgatory. These indulgences are derived from the "merits" of Christ and the saints, who do not need them, and who thus "pass them on" to those who do. For example, reciting certain prayers may result in a "40 day indulgence," which would "reduce the time" a person has to spend in purgatory by 40 days. The person reciting the prayer could apply the indulgence to himself/herself, or could "assign" it to someone who has already died. Certain prayers, actions, works, etc. generate a "plenary" indulgence, which also could be assigned to a soul in purgatory should a person not wish to "credit" to himself or herself. A plenary indulgence "wipes away" all time due in purgatory, and would make it possible, if one is assigning the indulgence to someone who is already departed, for the deceased to be immediately released from purgatory and "enter heaven." [This is in part why in Roman tradition the Mass is celebrated daily for the departed -- not just because in Scripture we read that "it is good to pray for the dead," even though it is not revealed in any detail precisely how our prayers benefit them, but so that those offering such "Masses for the dead" can reduce the "time" the "poor souls in purgatory" must endure their punishment, thereby hastening their "entrance into heaven" and their ability to "behold the Beatific Vision."
So the "merits" that make indulgences possible derive from the unused, superabundant merits accorded Christ, the Mother of God, and the saints.
As you probably know, it was precisely the issue of indulgences that sent Martin Luther over the edge in pursuing reforms in the Roman Church -- plenary indulgences were being offered -- "sold" -- to those who made financial contributions to the building of St. Peter's Basilica in Rome and other for other activities that involved the exchange of money, leading one reformer, Tetzel, to pen the his oft-quoted ditty, "Into the coffer the coin doth ring, and out of hell the soul doth spring."
With regard to the "energies" of God -- spoken of by such writers as Dionysius the Aeropagite and Palamas...
The "essence" of God -- that is, what He is in the very depths of His divine nature -- cannot be fully known to us. That is, as ones possessing the human nature, we cannot fully know or understand, especially on the intellectual level, the very innermost, divine nature of God. In this sense, God is "unknowable."
HOWEVER...
We precisely CAN know God by His "energies" -- that is, by the way He reveals Himself to us in time and space, in His creation, in one another, in His "tangible characteristics" such as love, patience, kindness, longsuffering, etc. God reveals Himself in this manner -- something the Psalms touch upon when we sing/read that the heavens and firmament shout the glory of God. In other words, we cannot know the very innermost essence of the Creator, but we can know the Creator by embracing His creation, which "reveals the glory of God."
Now, with regard to your question as to how "how the belief in indulgences could get in the way of Orthodox theology dealing with the Energies of God," I cannot say, because I cannot discern any way in which the notion of indulgences, which Orthodox Christianity does not share, and the energies of God connect. I suppose that one could argue that the superabundant "merits" possessed by Christ -- merits He obviously does not need for Himself -- could be, if one so chose, considered among His "energies," and that one could deduce that those who reject His merits -- unrepentant sinners -- somehow refuse to know God because they refuse to accept His "merits," or something to this effect, but the fact remains that, since in Orthodox theology there is no intersection between God's energies and "merits" -- in part because the whole "merit" thing is foreign -- there is no conflict since the "merit/purgation" thing does not exist in the first place. As I said, if someone chooses to consider "merits" as an "energy" of God -- which Orthodox Christianity wouldn't -- then one could, in the end, deduce that God's "energies" can only become effective or manifest if one chooses to embrace them, but in the end, this would be to say that God's actions/energies/activities can be limited by the human will and require ascent on the part of humans in order to be "activated," or some such bla bla. So I can't really say how belief in indulgences would get in the way of God's energies, since there de facto is no connection in Orthodox theology -- unless I missed something when I was in seminary.
I might add that, at least as I understand it, the whole notion of purgatory -- enduring punishment after death for sins that were forgiven, especially sacramentally, in this life, with genuine and sincere repentance -- stands in conflict with the image of God's forgiveness as found in the father of the prodigal son, who forgave his son with no strings attached, with no qualifications, with no conditions -- ultimately, the prodigal son's father did NOT say, "I forgive you, my child, since you are clearly repentant, and I will accept you back fully after you have worked three extra months in the field as punishment for taking your inheritance and blowing it, against my will and wishes and suggestion." If the father had sent his son off to the fields to "purge" the effects of his sin or as a punishment or as a "proof" that he was really repentant, then there would be cause in revelation to conclude that a state/place of purgation not only exists, but is required to "get into heaven." But this is not the image of God's forgiveness Christ reveals in this parable -- much less when Christ said to the wise thief, "THIS DAY you will be with me in paradise" instead of saying "NEXT MONTH you will be with me in paradise, since because of your thievery you have to spend 30 days in purgatory to 'purge' the punishment accorded to you for your sin, unless Mary Magdalene says three Our Fathers, three Hail Marys, and three Glory bes on your behalf and obtains a 30-day, or even plenary, indulgence for you, which would then make it possible for you to be with me THIS DAY in paradise." Get the point?
Hope this helps.