Reading many scientific studies that are done poorly, I am not convinced that you need a lot of formal training in a field to identify bad science. Many frauds and errors are blatantly visible in their data, which should have a given distribution but doesn't, or in their flawed analyses. Many others have several clearly uncontrolled variables (hint: if it's not in the paper, they didn't control it).

People of a given field will also often circle the wagons around bad actors to protect their own jobs and reputations. This introduces a very strong bias in the people who should be the most highly-informed on their own subject, and sadly makes them less trustworthy than people like Data Colada (https://datacolada.org/) who go beyond their own fields.