Doing one's own research
These days, when someone tells me they “did their own research,” I immediately suspect they have no idea what they're talking about and have no idea how to think critically. We know that Google and practically all other search engines customize their results based on what they know about the user and what most pushes their buttons. For that reason and others, sadly, “doing one's own research” is now code for falling prey to confirmation bias and being manipulated by online platforms and filter bubbles.