Aside from the racial and gender questions, there are other issues that time-travel shows rarely deal with and that Rewind
would probably have skirted. What about language? If the time windows can open anywhere on Earth, then statistically speaking, the ones that open on land are most likely to open in Asia, then Africa, then North America, then South America, then Antarctica, then Europe. And North America's only been Anglophone for the past four centuries or so. Plus, go back far enough, and nobody in the past will understand Modern English. So in principle, most of the places they'd go to would not be English-speaking lands.
Although I suspect the show would probably have ignored that and kept the windows focused mainly on the Western world in relatively recent history.