This is a very poor and completely irrelevant analogy. A mechanic’s sole purpose is to identify and fix problems with a car; customers come to him/her and pay him to do precisely this. The same type of role cannot be applied to a moderator on this site - we are not here to diagnose and fix your work, nor should you expect us to do so.
Would you expect the curator of an art gallery to sit down with every artist whose submissions have not been included in an exhibition to explain what’s wrong with their work? Or do you expect the editor of a magazine like 3D World to write a personal explanation to everyone who submitted work for a chance of publication but didn’t succeed, explaining why their image wasn’t included? If you answer yes to any of these questions, then in all honesty I’d say you have not only very unrealistic expectations of others, but also, to be extremely blunt, a rather inflated sense of self-importance in the grander scheme of things. With all due respect, the world doesn’t revolve around you. You’re just one of many, many people whose work is not accepted into the gallery on a daily basis; moderators are already sacrificing a good chunk of their spare time (hell, I’m writing this at 2:45am) to go through the submissions - to expect them to go even further and write lengthy explanations for every image’s non-acceptance is frankly absurd, especially when you consider that the person who casts the final no vote might not even necessarily have the same reasons for voting that way as the others who did.
Our WIP forums are there for critique. Why some people have such a huge problem with posting there is truly a mystery to me - I wish I’d had access to such a huge communication platform for discussing this stuff when I was younger; my work would be so much better today for it, because I’d have mastered the fundamentals even quicker and therefore moved to a higher level at a faster rate. But that’s because I have always been receptive to critique and discussion about my work, unlike some who are more intent on embarking on indignant campaigns at their imagined injustices instead of just picking up their Wacoms and getting back to work. Because that’s why we’re all here, isn’t it? Because we’re artists? Work for yourself, first and foremost, because your art is an expression of your ideas. And if your work doesn’t get accepted into some gallery that you submitted it to, then consider taking a second look at it or getting some outside opinions. It’s not hard. In fact, a lot of people whose work gets rejected do that on a daily basis.