What are the cons of flux welding?

Could you elaborate on the potential downsides of flux welding? I've heard it's a popular technique, but I'm curious about its limitations. For instance, does it require specialized equipment or training? Are there any safety concerns that operators need to be aware of? Additionally, how does it compare to other welding methods in terms of cost-efficiency and weld quality? I'd appreciate a concise yet comprehensive overview of the cons associated with flux welding.