Principles are ways of successfully dealing with reality to get what you want out of life.
Ray Dalio, one of the world’s most successful investors and entrepreneurs, cites principles as his key to success.
While feedback should be constant, reviews are typically periodic; their purpose is to bring together the accumulated evidence of what a person is like as it pertains to their job performance. If the constant feedback is done well, it will become like a constant review as the bits and pieces will add up to the whole. A review should contain few surprises, because you should continuously be striving to make sense of how the person is doing their job. If you think their job is being done badly, you should have been probing to identify and address the root causes of their underperformance on a case-by-case basis. It's difficult for people to identify their own weaknesses; they need the appropriate probing (not nit-picking) of specific cases by others to get at the truth of what they are like and how they are fitting into their jobs.
In some cases it won't take long to see what a person is like; in other cases it's a lot harder. But over time and with a large enough sample of cases, their track records (the level and the steepness up or down in the trajectories that they are responsible for, rather than the occasional wiggles) should paint a clear picture of what you can expect from them. If there are performance issues, it is either because of design problems (perhaps the person has too many responsibilities) or fit/ abilities problems. If the problems are due to the person's inabilities, these inabilities are either because of the person's innate weaknesses in doing that job (e.g., someone who's five foot two probably shouldn't be a center on the basketball team) or because of inadequate training. A good review, and getting in sync throughout the year, should get at these things. Make sure to make your assessment relative to the absolute bar, not just the progress over time. What matters most is not just outcomes but how responsibilities were handled. The goal of a review is to be clear about what the person can and can't be trusted to do based on what they are like. From there, you can determine what to do about it.