Agents get far too many submissions to reply to each one. Usually their website will tell you how long it takes them to get through submissions. It can take weeks or months.
If something can be read easily aloud, it has a "strong voice." Have you ever noticed that if you read something written by a friend or celebrity, you can almost hear the words in their voice? It's like that. Publishing is full of jargon. If you want to be published, you need to learn the vocabulary. Writing classes and books on the craft of writing are full of definitions. And then there's Google.
Agents shouldn't lean over backwards to help anyone that isn't going to make them money. Sounds heartless perhaps, but they need to make a living for themselves. They aren't teachers, and they won't coddle writers that aren't already their clients. If you want to be helped, don't look for an agent, whose focus is marketing. Look for a writing teacher or a freelance editor to get you to the point where you can be marketable.
If you cannot afford a freelance editor or a [high quality] writing class, then find the Query Shark blog and read every single post on it.

Writers! Don't be your own worst enemies!