But that's not what you are saying. What you are saying is "My style is the best at X" which is
at best a statement that needs to be proved - and can be disproved by counter example.
If you think that the implication that not having the best agency (or anything else) is in any way an insult or of itself makes other gaming styles wrong then you shouldn't be trying to claim your way of playing has the best X because when you do you are saying that literally everyone else is wrong. And you do not have a leg to stand on when your own feelings get hurt because it's pointed out that you are not at some theoretical maximum here and others can give more. It's you saying "Any other than the best is wrong" rather than "This is a valuable factor in a complex situation."
If only the style of play that is best at X is right then I can guarantee that your style isn't it
no matter what that style is. Humans are complex and "best at X" normally ends up being a
paperclip maximiser.
If you want to talk about something as used by the OSR community try using "OSR" rather than "Old School"? Otherwise you will get people like
@pemerton legitimately pointing out old school sources. Meanwhile OSR refers to a specific approach.
And to me classic Old School sandboxes have therefore and by that definition always seemed to me to have less agency than games run more like Fate where my characters are much more able to influence the setting. Classic sandboxes keep me detached from the setting and restrict my agency because my character does not move anywhere near so freely.
A good example would be the Fate roll to Create An Advantage using Contacts. In character this is the character finding who they need to in the town or city - but this means that the player gets to endow traits about that contact rather than pick from the half dozen or so pre-prepared contacts. My character can move freely in their area of expertise precisely because the setting is malleable and they are part of that setting. Play I expect from a predefined rigid sandbox (and yes I am calling sandboxes rigid here even if a whole lot less rigid than metaplot heavy games and adventure paths) would restrict my character in ways that meant they were less a part of the setting.