You wont be able to do everything alone, and with llm you can push the barrier so far that eventually when you will need to communicate, no one will understand what youre talking about :)
There will be no common framework to build on. Like imagine talking now to someone from ancient rome, they will not have an understanding for what most of everyday words you are using today.
its not about translation. its about the concepts. there was no concept or microbe, elcticity, gravity integral, rational number etc. so imagine everyone now would have totally different concepts that only they understand. how do you communicate without common ground.
For some things, you'll need to build a working framework from grounds up. Electricity or more complex maths would be an example. For some, it might be enough to repurpose the existing framework they already have. For example, microbes: if you're trying to communicate something about health and hygiene, chances are, the other side already has a half-decent framework built around malevolent spirits or taint, that amounts to the same thing in practice.
Or, just tell the universal translator to ELI5 it to the other person :). Or "explain like they're a caveman". Our UTs are fully capable of translating concepts between conceptual frameworks.
Communication and coordination are bottlenecks.