When the Coptic Church's theological school at Alexandria was restored in 1893 they determined to maintain the Coptic language as a liturgical language though it is extinct without native speakers.
As a Coptic theological seminary, there was a real fear that abandoning the Coptic language would result in a loss of Coptic authenticity and accuracy of the Coptic tradition which, of course, would have resulted to some extent if they had done so.
The training of clergy in the use of the ancient Coptic language isn't just an exercise in futility, but an important tool in maintaining the integrity of Coptic theology and culture through time.
So while, for a Copt, a thorough understanding of the Coptic language can benefit them in their relationship with God from the point of view of the Coptic tradition; there are tradeoffs. Difficulty for church members, new seminary students, and converts result in having to learn a "dead" language not to mention that "dead" languages do not usually carry the potential socio-economic benefits to individuals as learning a living language such as French/Spanish/Italian might.
I suppose ultimately, it comes down to the Coptic Church wanting to remain the Coptic Church and the Coptic language helps them safeguard that mission.
I'd prefer learning a Latin language (like french/Spanish/Italian or so) to learning Coptic, the relationship with God is easy, why do we complicate it?!