Someone said to me, "Your text is monotone in fashion" and I just simply can't wrap my mind around this statement. If I am wrong, that is okay. Assume it's a metaphor, can this make any sense?
Sentence length is a stylistic choice, and therefore not usually discussed on ELU, but Syntax is important for writing good English. Try introducing a few conjunctions.
When, if, although, since, after, because...
(Don't always use them as the first word) Use a mix of long and short phrases. Speakers do. Some writers stick to one sentence length, and that's monotony of rhythm.
Tenor, register is also treated as style, and avoided on ELU. Monotony of register is often a good thing. But in creative writing you will vary the words to suit the speaker. Some will insist on correct English, and others mayn't even bother to get the grammar they was taught. This is called Ethopoeia in nerdish.
Nam cum piratae persona suscipitur, audax, abrupta, temeraria erit oratio.
For when a person takes on the role of Pirate, their speech will be audacious, short, fearless.
Monotony of style can be broken up with rhetoric.
I don't have a sample of the writing that they used to base their opinion of your writing as being "monotone", which would help out a lot. I can only assume a few of the ways that they meant it, some of which are metaphors (which you wanted them to be).
- They were being polite and trying to help you and let you know that your style of writing is dry or boring. For example, they think that you don't use enough adjectives or onomatopoeias.
- They were trying to be insulting of your writing and in doing so used the adjective "monotone" to describe it. Which has a loosely attached, negative, connotation.
- They were ignorant of the word "monotone" and misused it to describe your writing.