Is it a good idea to join a multi-level/network marketing group?

I honestly do not know much about how it works. I only know the basics. I have to admit that I’m biased because I quickly associate these groups with scams, dishonest business, manipulation, etc. They tell you want you want to hear, and promise that joining them will make you rich. Also, their products are substandard (high price, there are better products out there than theirs, etc.) So, could someone tell me the good and the ugly sides of multi-level/network marketing?