In considering whether the Modern Greek language is a natural descendant of the Ancient one, I have complete confidence in replying in the negative. I have many reasons thinking this.

Although Modern Greek language is often credited or it often ‘credits’ itself, being a Hellenic dialect continuously spoken in the Greek family hearths, generation after generation, it doesn’t look to me it really happened. It was another place where this language has been continuously spoken: the Church.

Yes it’s been spoken from a limited number of middle class orthodox believers Ottoman families ,  of some high ranking Christian Church clergy and a very small minority of Christian educated [in the best case since the Byzantine Church artificially adopted the Koine (and not the Attic, like some people like to say) language for liturgic purposes. Other than that no one spoke Greek before Greece was a country .

The Koine itself was a semi artificial language, and was spread to the East mostly for liturgics and political and comercial purposes, and never represented the original language of the Hellenes, like it never represented the Hellenes themselves.

The exorbitant fantasy of the theory in which the Modern Greeks are Read more of this post