First of all, the characters and story are not interesting. I don't even remember most of the characters' names because they have basically no personality or anything about them that would make you relate to them or make them likeable.
The gameplay is awful. Most of it is just pressing two buttons, attack and healing. No interesting mechanics, just mashing of two buttons. Level design is 95% trash. The only place I liked was the vault overrun by super mutants, because it actually has some kind of a cool feeling to it and felt destroyed and empty.
Most of the time I don't even feel like playing a Fallout game. They could just slap different names on some characters and creatures and it's basically no longer a Fallout game.
Games of this series for me were always about a post-apocalyptic wasteland, a bleak, empty place where the remains of humanity are creating factions and trying to survive. RPG's where your choices shape the world around you in one way or another. Here all you have are dialogue options and the game is not really that open so you just traverse linear locations and kill hundreds of enemies by mashing two buttons over and over. The enemies also don't feel fun to fight. You just walk up to them, press attack a couple times, they die, repeat.
This game right here, is the absolute worst Fallout expierence you can have. I would put any other Fallout game above this one, even 76 and Tactics had atleast SOMETHING good about them. This game has nothing. It felt painful to play. Brotherhood of Steel does not contribute to the franchise in any meaningful way and is a really bad game in general.