What really changed my ideas about shapewear and foundation garments was when I grew an interest in vintage fashion. In the big view of things, it has only been quite recently that women of any size would go out in public without shapewear of some sort under their clothing. In the 1920's modern women liberated themselves of the corset, but then different shapewear to create that straight look (minimize the bust and hips) appeared. In the 30s it was absolutely essential under those new slinky bias-cut gowns and the more womanly, form fitting shape that appeared, and the silhouettes of the 40's and 50's can hardly be imagined without the shapewear that created them. It wasn't "cheating", it was expected.
Though we may be glad that women are no longer expected to always have on these sometimes constricting garments, I believe we also should realize the modern expectation that we should be able to look completely smooth and seamless in our clothing
without shapewear is an unrealistically over-demanding expectation in the other direction. As others have said, even the celebrities who have it as their
job to look appealing (and that includes intensive workout routines with personal trainers, diet plans with personal chefs, and teams of wardrobe people) make extensive use of shapewear.
My point in all of this is to say that if we; as women in general disregarding size, shape, or body changes as a result of weight loss endeavors; want to improve how we look in our clothes with shapewear, we should darn well do it, and shamelessly without any feelings of guilt or "false advertisement". We deserve to look and feel as good as we want to.
(I will note that the decision to go without shapewear for any reason is one I fully respect)