So what is your point exactly?
If a life form does not change its shape over time; no problem. You do not move into another house if your current house is fine do you? There has to be some reason (lower rent, more pleasant landscape, closer to the stores, etc). If there is no benefit in changing, why would you? And if the rate of reproducing of yeast was TOO slow, it would have died out. Since it didn't, we must draw the conclusion it has genes that can manage in its current evironment (and perhaps other environments too without having to change physical appearance!).
And if the calculations don't add up, we must find out WHY it doesn't add up. We should not throw Darwin's theory out of the window because yeast doesn't seem to fit into the profile at first glance. We should find out where the problem is. It is a question that needs an answer, not undisputable proof that divine creation is a fact...