I think this answer has to be qualified into first time players, returning players, seasonal players, and eternal players.
First time players will obviously be seasonal anyway…so endgame is gonna be anything post storyline.
Returning players would expect a bit more in this area.
For me as basically an Eternal player I expect to run things that can upgrade my characters equipment and abilities to perform the best in things like the Pits. True endgame is finishing the highest level pit if possible.