There are many reasons to hold on to liturgical English. One is the fact that only with thee/thou and ye/you are the differences between 2nd person plural/singular and subjective/objective (found in nearly all other modern languages, and in all of the old liturgical languages we are translating from), another is beauty, and perhaps most important is that liturgical English is a stable liturgical "dialect" or language that doesn't vary from century to century.
Anyone who is well versed in traditional language falls right into prayer and worship when the cadences and familiar verbage comes along. It doesn't matter if one is reading Cranmer's prayer book or modern Orthodox translations done into traditional liturgical English. And our great-great grandchildren will be able to pray with any of the above.
If you look at the main liturgical languages in use in the Orthodox world (liturgical Greek and Church Slavonic), neither is the modern vernacular, and both take a little effort to learn.
Precisely. And the same goes for Syriac, Coptic, Ge'ez, and even the languages of other religions--Hebrew, Arabic, Sanskrit, etc. When Rome was being threatened by the barbarians in 476, some Etruscan priests came forward to offer say some prayers in Etruscan--despite the fact that the language been extinct for probably 400 years by then. Religion has a natural conservative instinct that naturally tries to hold on to the ancient expressions.
My experience exactly when I re-encountered the 1928 BCP Order for Holy Communion after 15 years of the '79 and its trial-liturgy predecessors!