Most of my players are all community theater actors like me, so we all know what it means to embody specific characters to fulfill the narratives we are in. So I presume that in comparison to D&D players on the whole across the globe, yes my expectations would probably be considered "high". But for what I know of the people I play with and what kinds of characters they can and have done in the various plays and improv they have done... my expectation on the kinds of characters they could play that fit the narrative I put forth is within reason I think.
If we were going to perform a production of
Romeo & Juliet, we'd all know the kind of performance that was expected of us for the play. So if I offer up a game set in the Greek-inspired setting of Theros... my expectation that the interested parties would know and care enough about that setting and theme is not out of bounds. And thus they should be more than capable of making a compelling character that was merely a human hoplite, rather than an orphaned medusa who was stolen from their parents as a child and raised by a band of minotaurs on the slopes of a volcano to eventually be sacrificed as an offering of the gods until they swore a paladin's oath of vengeance against them and killed their captors before escaping to the nearest polis.
So yeah... my expectations may be considered "high".