Both the McRib and Soylent are intended to extract a price from customers in exchange for sustenance and a positive consumption experience. The McRib leans towards experience in its marketing and Soylent leans more towards sustenance.
The marketing of Soylent is certainly more active these days which isn't really that surprising as the product and company have developed from a concept to a full fledged and funded company. They're affiliating themselves with claims and experiences that may be unfounded, just like the McRib implies it's a delicious BBQ pork sandwich and not processed meat (pork?) shaped to look like rib meat or how car manufactures imply that purchasing a new vehicle will improve your life substantially. Customers will decide if their product matches their claims or if the product serves enough of a function to purchase despite the fact that it may not meet all of the claims it affiliates itself with (like complete food replacement... which is a marketing affiliation, not a legal claim). If you buy Soylent and get sick because all you eat is Soylent and you don't take the necessary precautions when completely changing your diet then you're in that category of consumer that might buy Axe Body Spray and think it's going to be the sole factor that makes you attractive to female models.
Marketing can be over the top and distasteful, but that doesn't relieve consumers from their responsibility to be skeptical of marketing claims and do their own research and basic risk remediation before purchasing a product.