The prophet Isaiah was quoted extensively not only by the Book of Mormon prophets but also by the writers of the New Testament and by the Savior himself. In fact, in our present New Testament the Savior quoted Isaiah more than all the other Old Testament prophets combined. Concerning the essential idea expressed in Isaiah 6:9-11 (and also in 2 Nephi 16:9-11), the Savior said the following concerning the people of his day:
Therefore speak I to them in parables: because they seeing see not; and hearing they hear not, neither do they understand.And in them is fulfilled the prophecy of Esaias, which saith, By hearing ye shall hear, and shall not understand; and seeing ye shall see, and shall not perceive:
For this people's heart is waxed gross, and their ears are dull of hearing, and their eyes they have closed; lest at any time they should see with their eyes, and hear with their ears, and should understand with their heart, and should be converted, and I should heal them. (Matthew 13:13-15.)
Also, the author of Acts quotes Paul as having said the following concerning Isaiah's words:
Well spake the Holy Ghost by Esaias the prophet unto our fathers, Saying, Go unto this people, and say, Hearing ye shall hear, and shall not understand; and seeing ye shall see, and not perceive:For the heart of this people is waxed gross, and their ears are dull of hearing, and their eyes have they closed; lest they should see with their eyes, and hear with their ears, and understand with their heart, and should be converted, and I should heal them. (Acts 28:25-27.)