>> It seems more practical to do work on stuff that could actually benefit from machine learning, as opposed to trying to solve incredibly difficult (and mostly theoretical) problems like discourse analysis.
The thing I am not sure about is how much it makes sense to attempt to create discourse analyses vs doing more "practical" work. The reason is that a complete and accurate discourse analysis seems nearly impossible. Having read through a few reference grammars and phonological analysis of various languages myself, it seems any rules linguists create are always wrought with copious exceptions and special cases (though certainly not all! There are examples of phonological rules that are very very regular across languages). Some of these analyses were extremely intricate.
I got the impression that many of them suffered from the mistake of trying to prescribe patterns to data that does not have any patterns.