I don't get Soylent's appeal, and I don't understand what unmet needs in the market it is meeting. My best guess, people that want to feel like they are "hacking" eating. Which is really just different marketing for a meal replacement shake.
1. It is way more expensive than Soylent powder.
2. It has too much sugar and too little of everything else. If you scale the calories to 2000 you'll have 400% of your daily recommended value of some nutrients and 50% of others.
3. It comes in annoying sizes (one bottle is only 240 calories, wtf?).
You could file this all under marketing and not be technically wrong, but it makes a real difference in the experience as a consumer.
If you go into a health food store like whole foods, there's a dozen or so other meal replacement options very similar to Soylent. Some soy free, some with exotic herbs and algae, some high protein, and all within the same price range.
Other replies have given me additional information which I'm going to go over. Your's was setting up a straw man argument.
files.soylent.com/pdf/soylent-nutrition-facts-2-0-en.pdf
Soylent is still low on protein for my tastes because I lift weights and I'm shooting for at least 150g a day.