I agree, some of the variety is not planned, but like I said, not cumulative changes will ever create new species, nor they have done in the past, as evolutionists think
The problem here is the duration science existed. It has been around for a few centuries at most. But the evolution process takes milleniums to operate. Meaning we can't access to live examples yet and before a long time.
The closest thing we have from evolved species are drug resistant bactery or pesticide resistant insects. They prove than changing is possible for living beings. Another proof are the fluorescent and bigger organism we were able to create. From there to thinking some modifications like the color of the skin, the size and other such little details can happen naturally (which, by the way, we can see in humans themselves - do you think the albinos came from other albinos?), you don't need great effort.
What keeps us from thinking than through cumulating, those alterations will end up forming new species from the ones already existing?
What is the difference between a cat and a linx? A fox and a wolf? A rabbit and a hare? And a bird from another? I'm not very knowledgable about it, but at first glance only the size and color seems to differ, and probably some minor other details.
On a slightly different matter, the apparition of legs as well as lungs and other organs needed for terrestrial live little by little may seems impossible. That's right, how could an animal with such primitive and inefficient organs escape a wolf or any other predator?
To answer that, you need to keep in mind than the first ones to ever aquire those caracteristics were also the first ones to get to land. Meaning no predator. So plants, not needing living food, were probably the first to get out of the water. Then came some herbivorous animals that could then escape their predators while still finding food. And finally the predator themselves could move onto land to escape bigger predator and still have some food. The faster runner would then escape the predator, the slower is catched, or the predator starve. The only one reproducing being the faster runner, the legs got optimised through years upon years of running.
Is such a way of thinking about how it happened that hard to accept?