Orthodox are known for not changing much. The most modern hymn that I can think of that we ever do is around 100 years old. The oldest go back so far, that I’m not sure anyone is really certain of the age. Our worship service, itself, has undergone very little change over the last 2000 years. If a Christian in the second century were to wander into our Church, except for his inability to understand the English portions of the service (or Slavonic if he were to go to a Russian parish), I think his only comment would be to wonder how come we’ve made it so short (Orthros through Liturgy on a Sunday morning is, at best 2 1/2 hours, vs. all night which used to be the case in the early days of the Church).
I found a great article at a parish in Arizona, that explains the Orthodox understanding of what Worship is supposed to be about. I only would like to add a few thoughts to the great information there. There is one element of worship, arguably a less important element, so I can understand why Dr. DeVyver didn’t really address it. That is the element of Catechesis. Although not so much the case within the Divine Liturgy, there is a strong element of Catechesis in some of the other services, most notably that of Orthros. Although the structure is largely the same from day to day and week to week (Sunday Orthros is longer, as it has a predominant focus on the Resurrection, and additional hymns were developed for that), the text of many of the hymns change in order to express teaching about the Saints or feast being celebrated on that given day.
The wealth of teaching in these services is not to be missed. Unfortunately, in this day and age, most Orthodox do miss Orthros, and thus miss the edification that comes from this service. Given the lack of knowledge of the faith among the Orthodox laity as witnessed by recent surveys, one part of the solution would certainly be attending and listening to the hymns and readings of Orthros. I only hope to see more priests pushing this among their flock.