I disagree - although this episode is one of the weaker ones, I do not think cartoons work very well without an underlying message, which shouldn't be rubbed into your face but rather mock the obvious failures and thereby reveal the sheer ridiculousness of it. There are plenty ways to do this, in a rather parental way like it is done in this episode or way more wacky, like for example in Southpark.

The problem with this episode is the resolution: It's far too obvious that Homer would represent the "missing link" between ape and man.

I rather have my problems with Family Guy: To me, it's just a loose string of more or less funny scenes that do not go anywhere. So to me, the jokes get old really fast - because it is too obvious that there will be an even more silly comment made, coincidence happen and so on. I liked some of the clips at first but the show itself didn't appeal to me.

I agree with you that shows like The Simpsons should not be seeking to make a point - they should simply make one in a more funny way than it is done here.