Standard evolutionary theory. Evolution did not have to take the path it took by any stretch of the imagination.

It didn't have to- but can't we discuss relative likelihoods of paths taken by evolution? It may be that the likely paths all look similar- the trajectory we took was in a 'rut' of broadly similar trajectories. It might instead be that wildly different trajectories are similarly likely- but that seems like something that you would need detailed inside experience to judge.

Consider an analogy to thermostats. The range of temperature fields that are present in a house over some time period is a tiny speck on the space of all possible temperature fields- but it's that narrow because the inputs don't vary all that much and there's a regulating system that tries to keep it narrow. Similarly, mutation could produce a far wider variety of life than we see now- but natural selection pares it down.