The answer to that is…it depends. Most commercial non dairy milks are not necessarily healthy: they often have very little almond in them, if it is almond milk, and most of the commercial types (whether it is oat milk or coconut milk or almond milk etc.) have other ingredients added, such as unhealthy oils including palm oil etc. So in my opinion, most are not very healthy. However, you can make healthier versions at home. If you want almond milk, soak almonds overnight in water (and then put them into the fridge and use as needed for the next few days). When you want almond milk, peel the almonds, add water and blend. You can add a bit of salt and maple syrup for more flavor if you like. Same with making cashew milk or even oat milk. But remember: none of them are nutritious if you use them in huge amounts constantly. You can use them in home made smoothies though as a base to thicken the smoothie . For example, i use my own almond milk, dates, frozen strawberries and half a frozen banana to make a very delicious smoothie.
If regular cows milk healthier? that also depends. Is the milk from grass fed cows? if not, then it is not necessarily a very healthy product. American dairy in general is not very good quality. That type of milk can be inflammatory or cause many intolerance problems. Butter is usually tolerated better (but it is only good if it is from grass fed cows).
Nowadays the food chain has been very much impacted by pollution, chemicals, pesticides etc. etc. We need to do our best to choose the healthiest foods we can from what is available.