One weird thing I noticed: Twitter wanted me to use an Email/SMS for two factor even though I have a registered TOTP token to log in to Twitter. I think that's been the case for awhile, not a new change, but still strange.
This is precisely how large, relatively well engineered services die if you leave them unattended for too long. The machine needs a little bit of oil every now and then and there are always new modes of failure found. Those then start to accrue to the point where they become user visible.