It’s a big field, I’m a lawyer and I know my one niche really well. I’m competent in that niche. Throw something at me like a criminal case and I’m worse than incompetent because I might let my arrogance eclipse my incompetence. It doesn’t help that the ethical rules defer to the lawyer, essentially, to decide if they are competent or willing to put in the effort to become competent for a given matter. Factoid: the only regulated legal practice in the US is patent matters. You have to be a patent lawyer to represent clients in patent matters. I guess the ethicists decided you can’t bluff your way through engineering, lol.