Funny. Run a quick search on the forum for any thread discussing vegetarian bodybuilding and you'll consistently see me reminding people that it's certainly possible. They're a subset of a subset of a subset, but they're there.
I actually said: "Almond milk is even less so; it's essentially almond-flavored water with added vitamins." That is accurate. Every almond milk I've seen on store shelves has none of the fiber, healthy fats, or (low quality) protein found in whole almonds. It's water with added vitamins and minerals. Trying to bring up protein powder is what I believe the kids call a strawman argument.
The bottomline is that the OP is a young, underweight kid asking for advice to gain bodyweight. You said: "I would try hemp milk or almond milk rather than cow's milk. Much more nutrient dense than cow's milk", and that statement is inaccurate and unhelpful advice for this situation.
Hemp milk or almond milk are not much more nutrient dense than cow's milk. They are lower in fat and significantly lower in protein.