He showed respect in this instance. If he had gone, you would be talking about how he forced his way in just to get a photo op. And you know the Bush’s wouldn’t have made a big deal about it at Barbara’s funeral.
And I agree with the reasons you gave for his not going. He said terrible things about GWB and Jeb, and I don’t thing either HWB or Barbara would have forgiven those. Yes, it was class to not go.
Also, protocol is that he would not go. His wife went, and was apparently welcome.