“From Darwin until now the big picture of evolutionary theory paints a picture of one species changing into another. It is an imagined and unobserved process.”
I will agree that it has not been observed since it happens over a very long time frame. I prefer to call evolution a theory rather than an “imagined process”. The fact that bacterial populations undergo a simple form of evolution makes the theory plausible.
Although one of the many things that makes evolution theory implausible is as follows.
The change in gene frequency you referenced earlier is a continuous series of very small changes. If speciation is true, it must be a trajectory formed by these changes. The changes occur a single locus at a time. Along the path of this trajectory, there is no distinction between species.
But all available real world examples of species show drastic differences between each of them. These large differences correspond with huge numbers of genes.
So what we observe is consistent with creation, not with evolution.