Mass effect is kind of railroad. Once you start mission, you must finish it, no leaving and coming back. Translated into ttrpg, once you enter dungeon, you can't exit. You either finish it or die trying. It gives you choices about which order or if you wanna do any side missions, but main story mission, that's pretty straight forward, you have some choices about what to do which will make final part harder/easier, some companions will die or survive, but final stretch is ultimately the same.
Mass Effect is very much like a pre written TTRPG adventure path. The main plot and major story beats are fixed, and once you start a mission it plays out in a directed, set piece way. You have meaningful control over your character, relationships, and some outcomes (like who lives or dies), but you can’t radically change or derail the core narrative. It’s strong on character agency, limited on plot agency. In TTRPG space, that's where player buy in comes. Players agree to engage with a pre written story, accepting the world, premise, and main objectives. They willingly limit their choices, knowing the campaign has a defined narrative, key events and a final goal set by the DM or module. Within that framework, players exercise agency: deciding how to approach challenges, interact with NPCs, and develop their characters but they don't derail the main plot. The restrictions aren’t adversarial. They create a shared structure that allows for meaningful decision-making, suspense, and dramatic payoff, while keeping the story coherent and satisfying. In essence, it's self accepting railroad. The railroad exists, but it’s voluntary: the structure enables meaningful character decisions and dramatic moments within a story everyone has agreed to tell.