The seaweed diet is just the result from a single study that has yet to be widely replicated. I'd caution against putting the fate of the planet into the hands of miracle cures until the scientific process can do its thing.
Even if the seaweed diet does help, the fundamentals of thermodynamics dictate that eating animals will never come close to the efficiency of eating plants, fungi, and microorganisms. Cows, chicken, and fish spend most of their energy living (to whatever extent spending every hour of your day in a windowless cage can be called living).
You do understand that's because it's not meant to - and it's not actually a valid comparison?
That's the point: the animals do the work of the processing and concentrating protein, fat, and nutrients/amino acids into a source that is arguably a perfect single food source for human consumption (high fat red meat, in this case); yes, your gut biome has to adapt for it, and yes, some lineages of humans will not have evolved with access to meat or benefit the same from having some or mostly meat in their diet like some other lineages of evolution.
It'd be more efficient to just consume sunlight, if possible, rather than waste it to the plants too - if maximizing for pure efficiency is the answer.
And let's also not be blindly virtuous about plants when looking at the primary and harmful method of agriculture also of monocultures. The Sacred Cow documentary also presents a good case for the benefit and need of cows, not in factory farms, for being a necessary part of the ecosystem/life cycle for soil health - healthy soil that is needed for plants; or do we ignore some facts and wait 50-200 years to see what disastrous problems we encounter because we don't include all arguments, perspectives, to manage from an all encompassing holistic view point?
Even if the seaweed diet does help, the fundamentals of thermodynamics dictate that eating animals will never come close to the efficiency of eating plants, fungi, and microorganisms. Cows, chicken, and fish spend most of their energy living (to whatever extent spending every hour of your day in a windowless cage can be called living).