This was a difficult but unfortunately absolutely necessary decision. Clearly nutrition comes above all else, but without some thought to the taste it would be simply undrinkable. To see just how bad it would be you could crush up a multivitamin (most are coated in maltodextrin) and add fish oil. All optimism for the future of food would dry up in an instant. Leaving out the small amounts of vanillin and sucralose would lead to an absolutely abysmal customer experience.
The amount of vanillin is too small to trigger the recognition of a vanilla flavor. This is not “soylent vanilla”, we just needed something to mask the bitter and fishy ingredients. The slightest amount of any additional flavorings will easily overwrite the extremely subtle flavor.
Sucralose is at a much, much lower concentration in Soylent than any other product to my knowledge that uses the sweetener. If you dislike the aftertaste of a specific product I recommend trying the ingredient in different surroundings. I am familiar with the distinct aftertaste of some sweetened products, and personally did not recognize it in our sample. The overall level of sweetness is extremely low. Imagine (or try) adding 19g of sucrose to 2L of water.
As for the concerns that everything artificial is bad, the evidence for the safety and usefulness of sucralose is overwhelming. A google search will yield equal parts pseudoscientific fearmongering, and reams of scientific data overwhelmingly showing it to be completely safe for consumption, even given a safety factor of 100. Even if not ideal, sucralose is certainly superior to a comparable quantity of sugar.
Beside user experience, I hope that we can also allay some of the baseless concerns mostly spread by the sugar industry that sweeteners are worrisome. Given the health burden imposed by the amount of natural sugar consumed in the United States, and increasingly in other countries with American soft drink imports, it would be a gain for the general populous to become more comfortable with sweeteners that do not impact their teeth, weight, or blood sugar, nor impose the vast environmental burden of sugar crops.