The answer depends on what counts as science. The so-called 'hard' sciences set the standard. This useful article lists the following five characteristics of science in the strict and eminent sense:
1. Clearly defined terminology. 2. Quantifiability. 3. Highly controlled conditions. "A scientifically rigorous study maintains direct control over as many of the factors that influence the outcome as possible. The experiment is then performed with such precision that any other person in the world, using identical materials and methods, should achieve the exact same result." 4. Reproducibility. "A rigorous science is able to reproduce the same result over and over again. Multiple researchers on different continents, cities, or even planets should find the exact same results if they precisely duplicated the experimental conditions." 5. Predictability and Testability. "A rigorous science is able to make testable predictions."
These characteristics set the bar for strict science very high. For example, is climate science science according to these criteria? I'll leave you to ponder that question. There are branches of physics that cannot satisfy all five criteria. But most of physics and chemistry meets the standard.
Am I suggesting that the only real knowledge is rigorously scientific knowledge? Of course not. Consider the knowledge we find in the first article to which I linked. There is no doubt in my mind that each of the five criteria the author mentions is a criterion of science in the strictest sense. (I leave open the question whether there are other criteria). Now how do we know that? By performing repeatable experiments in highly controlled conditions? No. By making testable predictions? No.
We know that (1)-(5) are criteria of genuine science by reflecting on scientific practice and isolating its characteristics. When we do that we engage in the philosophy of science. Since some of the philosophy of science gives us genuine knowledge about natural science, knowledge that it not itself scientific knowledge, it cannot be the case that all genuine knowledge is scientific knowledge.
That all genuine knowledge is scientific knowledge is the thesis of (strong) scientism. Therefore, (strong) scientism is false.