I don't have a qualified opinion on milk alternatives. Personally, I'm one of those lucky people who have very mild genetic lactose intolerance which is offset by good gut biome. So I enjoy milk in moderation (and I'm pretty crazy about cheese :) and the foodie part of life would be seriously degraded without butter ) and generally do not enjoy the plant substitutes purely on taste grounds, but I recognize there's a lot of people who do, out of necessity or by choice.
On the environmental impact, I have the same reservations. Say, "land use" is a terribly ambiguous metric - what does it even mean? Is that land used exclusively by dairy cattle? In what way, are they crowded into covered mudlots and never see sun their whole life, or is that acreage a nice lightly wooded space where they range and help manage undergrowth, and produce dairy and then eventually offspring that are allowed to partake and then maybe in the later life they graduate to expensive beef? There's been an episode of Chef's Table, one of the earlier seasons, representing a chef - I forget his name, but he's in some way co-running the Blue Hill at Stone Barns place in upstate New York, where he described how he rediscovered the eco-systemic way of managing the land, and that involved dairy cattle. "Emissions" are also suspect in the same way - yes, factory cattle produce excessive emissions, but maybe that's just bad technology and not the actual cattle's problem? People seem to be awed by the famous case of reintroduction of wolves to the Yellowstone and the subsequent abatement of the trophic cascade there, but why wouldn't we consider productive cattle in the same way?