I think UTs are bad for society because they make us less likely to question our linguistic biases.
Language is ontology. I've been learning the local Indigenous language, alongside Aboriginal metaphysics, history, culture, and law. Aboriginal language helps Me change My perception of the world around Me, by rephrasing daily life. With new words come new perceptions. I can't learn everything I've been learning at the same depth in English. A universal translator would stunt that development.
And I think that effect isn't just academic, it's societal. A whole world of monolingual people using UTs would be a world of people who don't know how to question the preconceptions that their language encourages. It would be a less intelligent, more culturally stagnant world.
Worse, under capitalism a UT would probably be controlled by corporations. Give corporations control of language itself, and society will decay. We're already seeing the start of this with words like "unalive" that develop from corporate censorship. UTs deployed en masse would provide new opportunities for propaganda and control. Imagine an immigrant in a new country who doesn't bother learning the local language, and just trusts Grok or ChatGPT to translate everything. It would be a good world for billionaires and a bad world for people.
I dread the day society integrates UTs into daily life.