While I believe the Orthodox hold Mary in high esteem and always have done, their antipathy to the Catholic Church means they view Catholic apparitions of Mary with unease.
I suspect they resent the idea of a Catholic “consecration of Russia to Mary” as a patronising insult to the Russian Orthodox Church.
It would be as though the Russian Orthodox Church claimed to have had an apparition of Mary in some remote village in Western Siberia, with three nearly illiterate Nenets kids as the heroes of the drama, with a message that the USA must be consecrated to Mary, and with two of the kids pegging out two years later from the Ebola Virus.
You could imagine the response of the Vatican and the US government to that message.
Frankly, when it comes to being the One Body of Christ, Christendom is one almighty mess. No wonder God’s allowing Islam to challenge us. I think He’s gotten to the point of disgust at our continued disobedience and endless divisions.