When you first start out in the home studio and home recording game most people don't have any specific training. They may understand stereo imaging and instrument placement, but these basic elements of mixing are complicated by all the other aspects of recording and mixing.
Take it from me, you cannot be objective about your own work - it is just not possible. So what you need to do is to give it to someone who will listen to it from a technical standpoint, having no regard for whether they like it or not, so you can get it reviewed without fear of any nasty comments about your pride and joy.
In my time I have had my fair share of nasty comments, and one just feels like saying "I don't care if you like it or not, just help me out on the production!" but of course people find it hard to divorce their subjective views on the work from a technical assessment.
The second issue is the time it takes to review properly. You have to listen 3 or 4 times at least and then make detailed notes before you can respond in a constructive manner. A four minute track takes about 30 minutes to go through if it has been done by someone with knowledge, the more inexperienced will produce more "errors" and thus it will take longer. People don't want to spend the time, so you end up with superficial comments.
So, what can you do? Well you can pay someone to have a look at it for you and provide a report back on the areas you should look at. Heed the advice well and you should, over time, get fewer and fewer errors. If you wish it can be musically reviewed at the same time. The beauty is, that with these days of broadband communications, this can all be done remotely. Send an mp3 file (of acceptable quality) or provide a link and away we go.
As I said, there are no fixed prices, but for a 4 minute track it's roughly £30 - send me a mail at the address below.
You can mail me here, email@example.com
if you want to ask me anything, I'll do my best to answer if I can.