The big difference is the marketing. Most of those products assumed you were either unable to eat or trying to lose weight. Soylent is roughly the same product but marketed to people who aren't interested in eating.
Think about people in comas, people who have parts of their jaw removed due to various oral and throat cancers.
If they can get the price down I'd probably try it too. Can't be worse than a protein shake as a post-workout supplement.
It's not exactly expensive, not that I'd recommend trying it.
Go for it, you will probably survive. Just not experiencing a very fulfilling life.
As someone who experienced the reality of tube feeding, it's not so easy as a single product. I was given supplemental amino acids, fish oils and vitamin boosters which were powdered and mixed with sterile water before use, alongside whatever the meal supplementation was during that day (things similar to ensure)
The fact that the manufacturers fear the regulators enough to slap disclaimers on the products and to carefully differentiate between over the counter product and specialist medical product should give Soylent users paise for thought.
Those companies, with dietitians and registered nutritionists and years of data from patients know that patients need careful monitoring.
By "dog food", I was referring to kibble and how it's made (and demonized in our culture because of it). Nothing more.