If you have left Islam, It does not prove that Islam is bad or incomplete. It proves that you have not been able to understand Islam correctly. If you are not satisfied with Islam and you have left Islam, but there also remains a fact that still 1.3 Billion Muslims in this World are satisfied with Islam. And they proudly call themselves Muslims. Why ?
Probably you might have got some doubts and you may not have clarified your doubts with an Islamic Scholar. Because , they are experts of that subject. I am sure if you find a genuine Islamic Scholar, Your doubts , if any , will be cleared.
Every Muslim can't understand the whole Quran and Hadith by his own. For Example, In Schools and Colleges, Even though we can read law books, medicine books etc , we don't understand everything just by reading only. We refer to some other thing , like More books, professors etc.