The UI is not so bad, it's the behaviour which is awful. I'm constantly finding myself logged into YouTube with my work account after logging into Google Drive

The UI is not so bad, it's the behaviour which is awful. I'm constantly finding myself logged into YouTube with my work account after logging into Google Drive to see a document shared to me by the coworker. Except after clicking on the link in the 'so-and-so shared a…' I just get a regular 401 'You're not allowed to access this content', because I'm logged in as a different account, but not provided an option to change accounts. I have three google accounts: work, 'Google-related stuff' (gmail, calendar, other google services), and YouTube, and I'm constantly logged into the wrong one. Google seems to assume that everyone has a Google account, and only one, and they're always logged into only that. As soon as you break those assumptions, things start behaving in unfortunate, unpredictable, and inconvenient ways. Even with their new ability to change between profiles, it doesn't work all the time, and when it fails it's overly confusing and arbitrary.