"More establishable" refers to something that can be proven or validated with greater ease or certainty. The antonyms for this phrase could be "less certain," "less valid," "unprovable," or "unverifiable." These words indicate that the idea or concept in question lacks a strong foundation, and therefore there is less evidence to support its legitimacy. Sometimes, this state of being less established can be an advantage, as it allows for more creativity, flexibility, and innovation. However, in many cases, it can lead to confusion, doubt, and mistrust. Therefore, it is important to carefully evaluate the level of establishability of any assertion or proposition, and to seek out multiple sources of evidence and perspectives.