There are a lot possible things to study in history. Naaturally, I suppose there are areas which don't get the attention they need.
(On another, I am not sure if I am breaking rules with this question, because it might be too general. If it is, I am sorry)
I tend to notice a lot of ignorance of communities that weren't enfranchised in their native nations, like minority religious groups and Roma. I have never seen an analysis of how big geopolitical events affected these communities. Would they have even noticed the collapse of major European powers like the Holy Roman Empire?
I honestly think that the more delicate areas of the long 19th century need greater research. Social history and history from below truly start in this period, but, as with lots of British history, from what I've read they're London focused.
A lot of the social crime studies are focused on the records in the old bailey, which means that, not only are quarter sessions ignored, history around the country is ignored too.
Also, the social impact of the industrial revolution has been well studied, but focused almost totally on the new, growing cities, and little has been done on the smaller industrial areas or the rural communities people were leaving.
In my own field (late antiquity, the centuries either side of the fall of the western roman empire / beginning of the middle ages), there's been a lot of amazing archaeological work in the past thirty years. But this work has so far mostly been used to answer economic questions, while historians of socio-cultural change tend to focus on written sources and ignore archaeology.(1) This means that there's tons of amazing archaeological evidence from late antiquity just sitting in the library waiting for someone to come to it with new questions and theories/methods.
In broader terms, there's a high demand for Asian historians in the US; if you're looking to make a strategic career choice and have time to learn the languages, your job prospects will be better if you study the eastern hemisphere.
(1) This is changing, but slowly; I can think of several dozen scholars effectively bridging social / cultural history and archaeology, but it's still a wide-open field.
I feel like Canadian history before the actual nation formed is heavily sensationalised, poorly narrated, or just plain misunderstood. Seems the government wants to downplay the extraordinary violence that took place here. Its like whenever I read Canadian history, it's always leading up to how the nation forming was the bread and butter or something. It just feels dull.
Though I'm not an historian.