I think the answer might be that you are
Each line contains at least one homophone and a re-reading of each line with the replacement word hints at the answer.
In vain I return to you,
In vein, I return to you,
The first homophone is present in a sense without being directly stated.
A few whacks and we got rid of the hare,
A few wax and we got rid of the hair,
This line makes more sense with the homophone replacements.
Can't we just pause for a minute?
Can't we just paws for a minute?
Not sure about this line, open to suggestions
What could we use to wine and dine? Mussels?
What could we use to whine and dyne? Muscles?
Muscles may be used to whine or produce a dyne (unit of force).
Sorry, we're all at sea aren't we?
Sorry, we're all at see aren't we?
Homophones are distinguished only by sight not by sound.
Pretending to be naval.
Pretending to be navel.
This is a reference both to a homophone being mistaken for another word and the idea of navel-gazing (connected to the sight in the previous line).
Is this just a waste of my time?
Is this just a waist of my time?
The navel from the previous line is located near the waist.
Homophones invoke a confusion between sight and sound. This line is a reference to confusion of the senses.
I'm through with you!
I'm threw with you!
Homophones are designed to throw you off.
The second half of the riddle suggests the you in the riddle might be eyesight and the entire riddle expresses the interplay between the senses and the confusion between them (especially sight and sound).