As someone who's going to school to become a teacher, it did kind of bug me that Lily was upset she was "only" a Kindergarten teacher. As if only being a teacher is somehow a horrible thing.
Aside from that I loved seeing The Captain again, and seeing the story get retold as we find out both Ted and Robin were inebriated was hilarious.
I disagree. Lily didn't go on a tirade about how teaching sucks.
I'm a teacher myself and I do have one of those days. I sometimes think about being a field biology scientist. It happens in every profession. I had teachers who thought about doing things differently. Some of them did briefly.
It's normal to have feelings like that. Really, the ship has sailed for Lily as an artist. Her internship in San Francisco went awful. And she liked that elephant painting. I think it won't last.