Just watching The Communicator (Enterprise).
Don't know if this is a controversial opinion, but I think they are risking far more contamination by going back to find that communicator than by just leaving it be. (And as we see in the rest of the episode, they take huge risks.) I don't think a world on par with 1940's level of technology would learn too much from a 2150's communicator. Their research equipment would probably be too primitive, and they'd even lack the required theoretical understanding.
But next time perhaps they should build in self destruct on such items that can be activated remotely. Just for cases like these.
I'd agree with you in the real world (as much as the real world can handle these sorts of things) but it was established in Future's End that 1970's Earth tech could reverse engineer 29th century tech so somewhere with 1940s tech would reasonably be expected to be able to get something out of a communicator from 200 years in the future I would think