I dunno.
We have quite a few Millennials in our Orthodox parish. They receive Holy Communion every week, so I imagine they are preparing to receive the Holy Mysteries by the same prayers, fasting, and Confession that we do. Some are also in the choir and/or are Readers.
It’s hard not to be a real Christian if you are a regular Orthodox. Our real problem is that we don’t reach out to the community to bring in people who are without Christ—i.e., most of the people in our Blue State.
Maybe we need to knock on doors (and I am including myself in that). The various cults do it a lot.