Removing verification was a major decline in usability. Verified accounts were good to know that you'd found the correct account for an organization or person you were looking for, but that's gone now. Verification was also a good first approximation that the account is at least somewhat notable, and not just some random online person, but that's gone now, too. With verification, Twitter used to be a moderately trustworthy source of news, now it's just a big pile of low-trust accounts saying things. You can certainly do the work to build your own trust network, but that's exactly what I mean by "decline in usability."