Evolution is an experimental science. If you don’t know this, you’ve been misinformed. The evolution of adaptations can be reliably observed. It won’t be long before this is routinely demonstrated in high school advanced biology labs.
Speciation can also be demonstrated over a period of a few years. Perhaps not in slow breeding animals, but then no one expects speciation in just a few generations.
Common descent is inferential in the same sense that criminal forensics is inferential. If you don’t accept this kind of reasoning, you better be prepared to empty all the prisons.