Anyone who undertakes the effort to study its nuances
has come to realize that, as all languages, the English language is a living, changing organism that cannot be preserved, only described.
A) has come to realize that, as all languages, the English language is a living, changing organism -> as is used for comparing verbs/clauses, But we have noun here. Incorrect.
B) comes to realize that, like all languages are, the English language is a living, changing organism -> "like all languages are" is incorrect.
C) has come to realize that, as all languages do, the English language is a living, changing organism -> Same as A. Incorrect.
D) will come to realize that, like all languages were, the English language is a living, changing organism -> Same as B.
E) will come to realize that, like all languages, the English language is a living, changing organism -> It is better.
So, I think E.