freshman in ML: how do you identify actually open research problems? [D]

Hi, I am a freshman who is trying to break into research. I got into a well known university research lab in my country for the upcoming summer, and the prof said I am "better positioned than numerous others" for hardware-aligned machine learning topics. I am facing a couple of problems, and I would like to know how seasoned researchers deal with them: How do you develop the intuition for what's open vs. what just looks open? When I look at a research space, everything either looks already solved or impossibly vague. There's no middle ground visible to me, yet. This bothers me.