This is a common criticism of the mainstream scientific conclusions made by creationists here on FR. Unfortunately it is completely uninformed as to the nature of the scientific process. The key thing about scientific theories is that they should make successful predictions about as-yet unobserved data-points. The theory of evolution has 150 years of success at that or scientists would abandon it. Predictions made by creation-science and ID, such as they are, invariably fall flat on their faces.
Scientists have not nor will they ever be able to "prove" evolution. But that isn't to say that shouldn't keep trying.
OK, what is one prediction concerning the future evolution of any existing species? Note: I won't be particularly impressed if the "prediction" has something to do with a virus "evolving" to another strain - after all, it would still be a virus, yes?
"The key thing about scientific theories is that they should make successful predictions about as-yet unobserved data-points."
OK, so what is the scientific community's prediction about the next step in the evolutionary process?