And that is fine: you can run a sandbox however you like. But there is also nothing wrong with running it the way I am taking about
No one said there was anything wrong with running your game the way you want.
My objection was to a specific example that was offered, and your response. That example is one I would say is a problem, for the reasons already stated.
Again, in this mode of play, the player simply isn't assumed to be able to set an agenda that extensive into the setting. You can certainly have the agenda of wanting to find your brother, but what is going on with your brother is under the purview of the GM. Obviously in a game where that isn't a case, it might be a dick move if the player is expected to have that sort of agenda. Why people can't even entertain the thought of this, and see how for lots of people operating under this style of play, it isn't at all a dick move, I really can't understand.
It's not that I can't entertain the thought of it. I absolutely can. I've played in plenty of those kinds of games. They're perfectly fine.
What I can't do is reconcile your idea that your described game offers a high degree of player agency when the idea of an agenda crafted by a player for his character either (a) shouldn't even be proposed, or (b) is left to the GM to simply negate out of hand if he decides that's what he'd like to do.
The play of your game seems to be to unleash the PCs into the world and watch them interact with elements you've crafted. They're free to do whatever they like, and to interact with the elements of the fiction however they like, and so on. That is fine.....I largely run my D&D game like this. The PCs do things, and the world reacts, and then the PCs react to that, and so on. It's fun and engaging and my group enjoys it.
Again, I don't think that running a game that has a heavy GM hand in such matters is a bad thing. If anything is bad, it would be to even allow the player to think that any agenda they had in mind at the start of play mattered at all. Just say up front "I know you wanted your PC to be searching for his brother, but I'm not really going to focus on pre-established goals like that. This game is about you using your character to explore the world I've crafted and to see what happens."
This. A sandbox doesn't care about dramatic arcs. Drama can arise (i've mentioned drama and sandbox) but no one has plot immunity (not PCs, not NPCS) and in a sandbox, the gm has full setting control. Those conditions shouldn't make the outcome I am talking about a surprise to anyone.
So this is partly the issue. You say that the GM has full setting control, but then you won't acknowledge that games that allow players some input on setting offer more agency. Instead, you shift to your take on agency and claim it offers an exchange of some sort. But I don't think that's the case.
To revisit your wannabe scholar character.....it seems you were okay with this goal because it fit with what you already had in mind, or already had a structure to deal with. And the outcome of how this would play out for the character was left to determine in play. I assume that they had a chance to actually succeed? Maybe I shouldn't.....was that the case?
Just to add one other thing here. I think it can matter in other ways. For example, I might really not like adventure paths, and that is a fine preference to have, but a ton of people like them. And it would be odd of me not to acknowledge or understand the sheer volume of players who find satisfaction in adventure path approaches.
Do you think that your chosen style offers more agency than an adventure path? Do you think you are attacking people who enjoy adventure paths if you say so? I've played in adventure paths. They can be perfectly fun. It's not exactly my preferred mode of play, but I also know what to expect when someone says "I'm going to run Horde of the Dragon Queen, want to play?" It's not going to be a high agency game.
Well, I am not the one discounting a whole style of play here. I am acknowledging the styles of the other posters, acknowledging their use of agency in their style. I am the one being told my style is a problem. Sure no one is free from criticism. But there is also an issue in these conversations when people just tear down your style, especially when they do so in a way that seems to ignore how huge swaths of gamers play the game. Literally every sandbox player I have asked has told me, the GM saying the brother is dead, is totally fine, not a problem. So if you do want to sit in judgment of a playstyle, I think it is odd to do so as you ignore the widespread sensibilities of those who engage that style.
Saying that your style doesn't offer as much player agency as another is not discounting the whole style of play. No style of play is a problem, excepting if the participants are not satisfied with it for some reason. A pure railroad may be fine for years for many players, or for a session or two for others. We all typically describe railroading as bad.....but for some folks, it may be just fine.