They're not even comparable. The Quest is a headset and two controllers you put it on and pick the controllers up, draw a room boundary and you're in. Works in any room in your house, completely stand alone.
Index requires you to install multiple sensors in a specific room in your house, and requires a connection to a desktop PC tower and fiddling around with Steam to play.
I think the FB account requirement is incredibly dumb from Oculus (Don't understand why it couldn't just be a shadow account like Insta/Whatsapp which everyone seems fine with weirdly) but really the product their offering is entirely in a class of it's own for a fraction of the price a normal VR setup costs and a fraction of the hassle.
I think if the market was different and what they were offering wasn't unique I think far fewer people would care and we'd all just buy different headsets.