This question was inspired by Tacitus. The Roman empire having historians means there must have been significant development in the historical method since then?
Is this an easily answerable question? Did historians of the past focus on specific things? Were these societally inspired values?
I'm sorry of this is too broad a question, mods feel free to remove it if it is. For specificity maybe a compare and contrast of ancient history versus post-Enlightenment history?
Yes! This is a well-established field, called historiography. The main aspects of historiography are analysis of historical writing trends throughout time, instigating factors behind them, and perception of history.
In practice, this involves a fair amount of categorisation - into "genres" such as political history, economic history, etc, and tracing changes through those themes - but also in periodisation. Hence concepts like ancient historical writing (usually implying writers like Herodotus or Thucydides), versus say Whig History (with the likes of Edward Gibbon). Whether you agree with the lines drawn or not, the importance of recognising differences in goal and concept of history-writing is vital for understanding these works as primary sources, as well as looking for credibility in more contemporary sources (such as teleological tendencies in some cold-war era writing, or more obviously the social darwinism present in a fair amount of histories and ethnographies of the 19th and early 20th centuries).