I dunno about its changing popularity, but like Expert Sexchange before it, I actively avoid Quora. It was the first site I added to my Google Personal Blocklist, and the reason I installed the plugin. Their unsubscribe form is (or was last I saw it in 2015) a nastier piece of work than I could imagine, even if told: Come up with the most annoying unsubscribe form you can. Make it really hard to unsubscribe from ever…
On mobile, they make you install their app to look at anything at all. Any company that needs dozens of "dark patterns" and tricks to stay afloat probably shouldn't exist. LinkedIn is the same.
Yeah, no thanks. I don't think looking up my password just to sign in is worth using the app on mobile.