Man cannot live by bread alone.
The OP asks if man can be changed:
The man cannot live by bread alone.
Men cannot live by bread alone.
The question is understandable and reasonable, because there are other contexts in which a noun plus definite article is used to describe that item in general.
In the last fifty years the computer has changed the world.
In the last fifty years computers have changed the world.
These two sentences are both OK and they both mean the same thing.
(Note that the computer can also refer to a single particular object: The computer in my home office is old and needs to be replaced. Whether the noun has a general or particular reference can only be determined by context.)
So with these notes in mind, let's return to the original sentence. I would say that the proposed changes are not suitable here, and it's because of the special background to this particular sentence.
As noted, man cannot live by bread alone has a history. It is a sentence from the Bible:
Matthew 4:3-4 (KJV)
3 And when the tempter came to him, he said, If thou be the Son of God, command that these stones be made bread.
4 But he answered and said, It is written, Man shall not live by bread alone, but by every word that proceedeth out of the mouth of God.
You will notice that the language overall feels old fashioned because of course it is. It is the language of Shakespeare, the language of the sixteenth century. But because this sentence is from the Bible, and even more so because it is a well known story from the life of Jesus, it has taken on a proverbial element. We can see that from the interpretation in the OP. There the saying is applied to social themes such as art or music; in the Bible it is applied specifically to the spiritual food that we receive from God's word.
So can you change it? Technically yes, but you need to understand that you are changing a proverb, not just a sentence. When I read this...
The man cannot live by bread alone
...I immediately think of this...
Man cannot live by bread alone
...and I think that the writer must mean something different, because he is intentionally changing a well known saying.
This is why modern translations either retain the proverbial flavour of the King James Version (see the New International Version [NIV]) or create a completely new style of gender neutral translation (see for example the New Living Translation [NLT]).