What is Player Agency?

[kyoryu]

That's the sort of discussion that has to be had before even Session Zero. The players exercise their agency in this case before the campaign even starts, by deciding whether they want to take part in that sort of campaign. Those who sit down at the table to play have agreed shape/restrict their characters' decisions such that they do not "naff off", to play characters who won't "naff off", etc.

Exactly.

I'm a high-agency kinda dude. And nothing will piss me off more than telling me there's actually agency and then leading me down a linear game. Nothing. If you want to play a linear game? Great! Go for it! But be honest about it and give me the choice of joining or not. I may decide to anyway.

The fact that agency isn't important to you, or to some players, does not mean that it is irrelevant or not important to other players.