I definitely believe in evolution, but wonder if maybe something is missing, especially when it comes to the sort of cross-species changes you’re discussing.
For example, it's very hard to imagine the grand canyon being carved out from water eroding the earth every time it floods little by little. But you can intuitively still get how that works. And I think the basic idea of natural selection is pretty intuitive. Whatever can't survive doesn't reproduce. You can imagine how that simple rule (of course it's more complicated than that) could lead to life to spread out, and adapt to many different niches and take all sorts of forms.