Generally the purpose of -lent foods is simply to provide a healthy option for people to replace any number of meals with. The reason so many people say Huel, for example, has so many health benefits, is because of its complete nutritional makeup. Many people are deficient in some micronutrient or another, and by following a -lent diet that provides everything you need, you minimise the risk of such deficiencies (although you don’t eliminate it altogether because RDAs are based on meeting the needs of 97.5% of the population, not 100%). For those who are already receiving at least 100% of their requirements for every nutrient, there are fewer noticeable benefits (though some still exist).
The main benefit aside from micros is, in my opinion, easy monitoring of Caloric intake. Many Huelers and followers of other -lent diets have been able to lose significant amounts of fat, leading to an altogether more healthy life. In my experience (and I haven’t used Huel extensively as I make my own recipes), most -lent diets, especially those low in GI, will keep someone satiated for a decent amount of time. As such, a Calorie deficit on a low GI -lent generally has less cravings that a high GI equivalent. In today’s world, many of the foods we eat on a regular basis are high GI, which can make weight loss more challenging. To the contrary, with a low GI -lent, you’re more likely to stick with the Calorie deficit, and this is what leads to the weight loss.
However, Huel isn’t a weight loss. It has a lot of protein, which means it can also be a powerful tool for muscle growth which can also make you healthier. It’s also very easy for maintenance.
However, assuming you’re already receiving all of your nutrition and are of a healthy weight, the main benefits of any -lent will simply be the convenience factor - they don’t take long at all to prepare, and for their level of convenience and nutritional completeness, the cost is, in my opinion, justified. You can make similar recipes cheaper if you’re willing to use your own recipes, but this takes longer to prepare and, unless you come across a good recipe, they’ll likely not be as tasty as the commercially available options. So overall, no, Huel is not a super fuel - nothing really is (except arguably some potentially lethal cocktails of supplements that make you feel amazing but come with a lot of health risks) - but it can bring about big health improvements to those who aren’t already healthy, and does so in a very convenient and reasonably cheap way.