What agents mean by 'not quite for me'

'Not quite for me' is a real answer, and it usually means exactly what it says: the agent could not see themselves selling the book with conviction. That is not a comment on quality. It is a comment on fit, and fit is the whole business.

'I didn't connect with the voice' is more specific than it looks. It generally means the prose worked but the narrator did not hold attention across a long stretch — the most common cause of a request that ends after fifty pages.

'The market is difficult for this right now' is the only one authors should treat as weather. It changes, it is not about your sentences, and it is the single best reason to keep a submission list long.