I don't think the content of the comments in this thread is limited to ML. I think there is lot of applied math research out there (almost all of it?) that hard

I don't think the content of the comments in this thread is limited to ML. I think there is lot of applied math research out there (almost all of it?) that hardly anyone outside of academia actually reads. I think there's some useful stuff but my impression is that research papers are mostly dead ends so I stick to graduate textbooks. Maybe other people have other approaches? I'm not a math researcher so I don't need to be at the cutting edge.