“That reflects the limited role of chance — pretty small.”
I think you’re seriously underestimating what chance is accomplishing in the theory. Without the millions or billions of random mutations to provide new versions of genes, there is no development in the organism. Natural selection merely selects the most “fit” variations, but it is the random chance that provides the raw material, the variations themselves.
There’s also random chance involved in the conditions those variations will encounter, which are key to whether they will be selected or not. So there is random chance dictating both parts of the process. Once you abandon any intelligent intervention in the process, what is left but random chance?
Oh yeah, the chance is the base. What mutations are successful are not chance. That’s my point but as you say, without the chance mutation you have nothing.