But u know how to become archmagister of telvaniI don't think open world needs arbitrary linear restrictions. Often games that have them could have been built without them. Ie there's nothing wrong with allowing player becoming friend of ashlanders before main quest for example. Neither I am fan of quest doors, chapter locked content, etc.
I think New Vegas did it more or less ok, you can interact with any faction freely there from the beginning of the game.
I don't see these things as arbitrary because they make sense in the game world. You can visit the ashlanders before the main quest, you just don't know how to become friends of them because nobody told you (your character, not you from having meta knowledge) or even that there is a way to do that (again, lack of knowledge).
New Vegas isn't any different actually, you can go to various factions' places but you can't bring up topics you don't know about.
Leave whys and allow player to interact with things they find
Meta just makes player run unnecessary around your game and wastes players time
Player will make up why or how they want to be bros with ashlanders first themselves, dm not required