This is tricky because who is the authority to declare something scientific or not. Science is not a definitive set of knowledge. It is a systematic approach to explore and explain our physical world. Scientists speculate on the nature of things and propose a hypothesis that try to explain the observed phenomenon. Then they set up an experiment or study to test the hypothesis. If the experiment is successful and can be repeated, the hypothesis is believed to be true until someone challenges it with a better explanation and experiment.
In the sense that TCM provides explanations of health and sickness and the fact that it can be applied repeatedly, it is scientific. TCM has been practiced in China and other Asian countries for thousands of years and is still vibrant in these countries and other communities where Conventional Western Medicine is readily available. It definitely had passed the test of time. However, TCM does not have the precision and mathematical feel we commonly associate with modern science. It is difficult to do controlled, randomized or blinded test of Western Medicine in TCM because it operate in its own paradigm. However, just because something is not precise or mathematical does not mean it is not true or not functional. Many social sciences also face similar challenges to appear as precise and mathematical as physical sciences. So TCM as a medical system is repeatable and useful, even though it may not appear “scientific” enough.