Some texts are read often but never really read. These might be texts that occur frequently in anthologies or reading lists: clearly there is a consensus they are important, but you might look through the bibliographies and find relatively few articles, or find that the articles about this particular set of texts do not consist of very close or deep readings. There are plenty of opportunities for very good work even on texts that are in plain sight. I've never found a really, really great reading of Lorca's duende leture, for example. Sure, everyone refers to it or quotes from it, but nobody has really taken apart its rhetoric, explained how all its allusions work with and against one another. So if this is true for one of the most famous texts of one of the most famous writers in my field, you can imagine that there are many other less frequently studied texts out there.
What I found with my Lorca book was that nobody had read Langston Hughes's translation with a critical eye at all. Nobody had done more than simply mention that Hughes had translated this book.
I get frustrated when graduate students want to do the same old thing, replicating other peoples' work, when there are much fresher research opportunities in plain sight. I'm seeing a lot of possibilities for things in Spanish American poetry that people have barely touched. Maybe I'm just better at seeing things than other people are, but a lot of these things are pretty obvious. I think they call it low hanging fruit.
Other times I get a semi-brilliant idea and give it to a student. By semi-brilliant I mean something that I know I could use to write a publishable article with no problem. I imagine what i would do with this material, and then I get a paper from the student that falls flat. This shows that it is not just taking the initiative to seize an opportunity, but also the capacity to see what's distinctive or interesting in the material. I still haven't learned the technique of teaching someone how to do that. I haven't solved the mystery of why other people are not like me.