They're probably not really trying to come that close. If you drink almond milk expecting it to taste like milk, you'll be disappointed but if you drink it for what it is, not expecting it to taste like milk, it's fine.
I agree with you completely, but the marketing and narrative around these products really invite the comparison.
Sadly they need to cater to a audience that craves familiarity and fears change.
Considering someone went through the trouble of inventing, manufacturing, and marketing them when milk was already there, I expect them to taste better.
I'd argue we shouldn't always optimize for taste. I drink a mix of plant milks and grass fed milk (mostly I use it in baking or yogurt making.) I buy for sustainability, taste, cost, and ethical animal treatment reasons.