Nobody said such a thing. I did ask what the alternative is. Going public isn't an alternative. That's what is happening. Figma is being transferred into a public trust. And that is the worry expressed with respect to its future, because the general public has no reason to care about the product and will not act in the interest of the product.
Anti-trust could, in theory, do more to prevent the general public from not caring about the product they control. The problem is that laws (where Figma and Adobe are located) are prescribed by the very same general public, so you have to convince them its a good idea. And if you've done that, the law becomes largely superfluous because at that point they're already on board and will act as such on their own accord.