As mentioned before, endless possibilities aren't realistic for butterfly effect games, but the player should still be given some semblance of control in how they want a narrative to span out. And while Fallout 4 wasn't exactly like fellow butterfly effect titles, it still gave players the option to make choices that would effect the game's ending. At least, a select few options anyway...
You, as the vault dweller, eventually had to choose a faction to side with. Whether that was the Railroad, The Institute, The Brotherhood of Steel or something else was entirely up to you, but for the sake of context in this argument,I will mention that I chose the Railroad. The final campaign mission involved us liberating synthetic slaves from the wasteland's Institute, which I thought was great. It brought up a valid question of "if a robotic life can think, act, and feel things for itself, does that constitute an individual life?" The Institute said no, but the Railroad said yes. So I was up and ready to take arms and liberate the slaves from their prison!
However, my problem was when the Railroad suddenly decided to blow up the Institute and effectively kill everyone who happened to be living in it that wasn't a robot. I wanted to choose not to do that, but by that point, it was too late. I couldn't suddenly decide to rebel against the Railroad for wanting to kill innocent civilians who weren't synths, or for that matter, blow up a place that could bring the world back from the brink of the apocalypse. I was given no real free will to decide "I want to free the synthetics, but the Institute must also survive for the betterment of mankind." Nope, the best hope for mankind just blew up right in front of my face. Perfect.
This could be chalked up to oversight from Bethesda, but it perfectly showcases how there's still ultimately no free will to play the games however you see fit. You just get a few choices to make, which are ultimately met with a point of no return. And that's very disappointing. Does the Mass Effect 3 ending ring any bells?