Diets don't work long-term. To maintain weight loss, there needs to be a lifestyle change that you can consistently implement your whole life.
Keto is cutting out an entire macronutrient. The more restrictive a diet is, the harder it is maintain long-term. This is the type of stuff that eventually causes people to fall off the wagon, and go back to their old habits.
Are you never going to eat bread again, every day of your life until you're 90? Same thing with intermittent fasting; are you never going to eat after 4PM again until you're 90?
If keto works for you long-term, great. It works for some. But what happens to most people, is they lose a lot of weight in 6-12 months, then fall back into their old habits and regain it back.