I think you will find there are a number of legal systems that don't require a professional. Tribal and religious courts that are older than most nations have long existed for the same purposes and require only an understanding of the mores, traditions and yes, Laws of a particular group. A person who is more experienced in dealing with these courts may have a better chance of success but I don't think you would be able to call many of them "specialized professionals". It is only when the Law of a group or nation has grown so byzantine that it almost impossible to live a life without violating some aspect of it that you will find the necessity for a professional group to manage the complexity.
In many "modern" sovereign states it has become common to pass laws with thousands of pages that have never been reviewed or considered as a whole. New laws often flagrantly and purposely contradict existing laws. Some are passed with the sole intention of having an excuse to stop and detain people when it is convenient, some are passed for political gain, and some are passed for reasons known only to the few people who secreted them away in an omnibus of unrelated legislation.The fact that modern law is so incomprehensible to the laity is a testament to it's dysfunction, not a justification of its existence. Ignorance of the law is no excuse, but when law itself has become so incomprehensible that even attorneys and judges can scarcely decipher its intent with regard to the common, good can any of us claim we are not ignorant?