The most important unsolved problems in ethics
In 1900 the mathematician David Hilbert published a list of 23 of the most important unsolved problems in mathematics. This list heavily influenced mathematical research over the 20th century: if you worked on one of Hilbert’s problems, then you were doing respectable mathematics.
There is no such list within moral philosophy. That’s a shame. Not all problems that are discussed in ethics are equally important. And often early graduate students have no idea what to write their thesis on and so just pick something they’ve written on for coursework previously, or pick something that’s ‘hot’ at the time. I don’t know for sure, but I imagine the same is true of many other academic disciplines.