The biggest difficulty vegans have is getting enough cobalamin. Meat tends to be a pretty good source, other sources may be unreliable. Luckily, things like peanut butter are full of insect parts, so vegans can claim they are being pure while at the same time cheating and getting vital nutrients.
That’s not difficult at all, and in reality if we ate meat just once a week, then not only would our health massively improve, but the environmental impact would be tremendously beneficial for the earth. This could be achieved if humans slowly ramp down the frequency of meat consumption over let’s say a 20 year period.
In reality this will probably not come to pass, but not all is lost: we are on the cusp of developing synthetic meat, not from sentient animals, but lab grown. if science can find a way to create this new meat without many of the harmful chemicals present in natural meat (harmful when consumed in excess that is) then that will be a great ethical balance where animal suffering could conceivably be completely eliminated, widespread farming areas are reverted back to their more natural states, the vegans can stop hassling the rest of us with grissly documentaries, the steak eaters can have their steak, emission of greenhouse gasses that cause global warming will be reduced