I took it as a very interesting and profound discussion about the role of games and fantasy in our lives as adults after playing it from a different perspective as kids. The dialogs during the ending are very well thought and thought-provoking. The role of Elaine in it is special.
I loved the whole game, but the ending brought it to a complete new level for me. It’s probably something that I’ll want to play again a few years from now.
But really, Ron Gilbert always wanted it to be critical and at least a bit deconstructive of all the pirate tropes: Guybrush never gets taken seriously as a pirate, the way in which he pirates is bizarre and unglamorous, and the dialogue follows a sort of knowing "NPC normalizes any choice the PC makes" railroading back into the puzzle gameplay. Gilbert just got more clear about doing that in the sequels, and I think Return is a great capstone to that.
“It’s a game lul” isn’t an ending. It’s an escape from the criticism both inward and outward that would result from a real ending.