It's kind of funny that the canonical ending of Fallout 1 was

The Brotherhood of Steel helps the other human outposts drive the mutant armies away with minimal loss of life, on both sides of the conflict. The advanced technology of the Brotherhood is slowly reintroduced into New California, with little disruption or chaos. The Brotherhood wisely remains out of the power structure, and becomes a major research and development house

And in Fallout 2 they're barely in it. Only in the late game giving you some cool stuff to use against the Enclave (implants, power armour).

I wish factions had been allowed to fizzle out and new ones arise, just like how Fallout 1 had the Union of Atomic Workers who were already pretty much wiped out by the time you enter the scene.