My personal view on this is that the Canadian immigration system is extremely clear and straightforward; unless your case is a tricky one, you feel uncomfortable using a computer or scanning documents, or you are really bad at following instructions, there is absolutely no need to hire an immigration consultant or lawyer. For most of the questions you see around here, you can easily and clearly find the answer on the CIC website (e.g. do I need to submit PCC? do I need to upload all the passport pages or just the bio one?) and most of the rejections are due to people not reading carefully and following instructions (e.g. expired IELTS, forgetting to upload passport (!!)).
The trickiest part is getting the job reference letters in the format CIC requires and it is tricky not because the instructions are not clear but because that's basically the only document that is not under your entire control.