Hi Spartacus and welcome to the forum.
Obviously it is easier to be vegan in some places than in others. Being aware of the health risks associated with the consumption of milk, by infants and adults alike, I would choose not to expose my child to that risk. Unfortunately there are a lot of humans on the planet, and feeding us all, by whatever methods, unfortunately does involve the destruction of habitats, as the population of the planet continues to expand.
As far as infant formula is concerned, I see the use of soy formula as more ethical and less damaging to my child's health than feeding him or her cow's milk. Indeed the WHO has estimated that as much as 75% of the world's population may be intolerant to cow's milk. It does make sense, since it is meant for baby cows, not for baby humans.
If we continue to rear and use livestock for our own purposes, this involves a greater use of resources than would the adoption of a plant-based diet.
You constantly mention soy; many vegans are actually allergic to it and do not consume it as part of a plant-based it. It is not essential! I consume very little soy, if at all.
Vegans are against the use of animals on ethical grounds; ultimately each and every one of us makes our own decisions based on our own conscience.