Everybody's weight loss journey is different. What doesn't work for you might work for someone else. The principles of weight loss are the same regardless of what diet, group, fad, whatever route you choose to get from A to B or Big to Small (B to S? lol) doesn't matter so long as you get there and you're able to sustain it.
Fitness influencers have an ulterior motive to put you off slimming groups and other diets and products... They want you to think they're the only viable, credible option. Most of the time, these fitness influencers have no qualifications or real-world experience, in other words, they're neither fitness professionals, healthcare professionals nor have most of them ever carried an additional pound too much of fat on their body in their entire lives. How on Earth could a skinny person who has never made it over 65kg tell you how to lose weight? They just won't get it.
Weight Watchers, Slimming World, Fat Fighters (from Little Britain), the principle behind them is accountability and support, fettered with their own individual flavour of low-calorie products they want you to buy. They don't promote these products to be a magic weight loss drug (stay clear of those too!), they're simply a means to an end, much like your Slimfast, Herbalife, Juice+ etc. They all serve the purpose of assisting you to maintain a calorie deficit. Ultimately, it is by maintaining a calorie deficit and making sure your diet is balanced, even in deficit, so that your nutritional needs are being met whilst (and more importantly so) you're in a deficit. By maintaining a calorie deficit whilst maintaining our individual nutritional requirements, weight loss is GUARANTEED. Keeping it off is a different story though, to ensure sustainable results, first we have to achieve our maintenance calories and cement this as a habit before we engage with a calorie deficit, otherwise we just end up going back to eating how we used to eat and over time, we gain all the weight back again.