We may always try and invent our own rules and limitations for the UT tech even when we have zero idea of how it works - the evidence from the episodes allows us to establish such rules and limitations for warp drive, transporters and phasers easily enough even when those are fictional and contrary to modern scientific knowledge.
The problem with the UT is that even the tiniest thing it does is already fundamentally magic; it's very difficult to establish limits when the 1st Rule is "the possibilities are endless!".
This doesn't mean the UT would be particularly unrealistic, though. Computing would have been pure magic to us half a century ago, and even today the limits of its applications elude us, but it's not fiction, and in many ways surpasses fiction as far as limitless technologies go.