Of course proper milk is superior to oat milk.

In terms of ecological footprint it really isn't. There, cow milk or any other animal milk is waaay worse than oat milk.

Furthermore, doesn't oat milk usually have a higher shelf life than typical animal milk like those from cows?

Lets not conflate convenience with nutritional quality.

As far as I know the one thing that cow milk has in terms of better nutritional quality compared to oat milk for example are high quality proteins, covering all essential amino acids. However, if you are not dependend on that intake of protein by drinking a glass of milk each day, due to other protein sources in your diet, then there is not really much more value to cow milk. Since soy milk has a higher amount of protein than oat milk, one could also prefer that over cow milk, which would still lower carbon emissions. Not as much as with oat milk though.