They want to make their little OS inside your current OS, so that's it, they introduce accounts, users, apps, notifications... Meanwhile most people (including me) just want to browse the damn open internet.
To be fair, the trend of the browser usurping the OS has been going on for years. Any browser that wishes to stay modern and competitive has no choice but to leverage the inner-platform effect to a full extent.
Just don't sign in? I don't feel being pushed into anything. If you're annoyed by that new button near the window management buttons, there's a chrome:flags thing to disable it (enable the new avatar).
The new Opera has the same engine of Chrome and none of the inconveniences. I'm using Firefox as primary browser and Chrome in another virtual desktop to work in Google Drive because it's a little faster (maybe too many extensions). I replaced it with Opera and it works well. I have no idea if it can use Chrome extensions, never installed one anyway as it was a single purpose browser.
Chromium doesn't opt you out of linking the browser to a google account. Opting out of linking the browser to a google account is called "not doing it", because it's an optional step anyway.
Also, chromium seems to be getting less and less care from google now. See this bug for example which prevents using screenshare in hangouts: https://crbug.com/416856
I'm not sure that's totally true – the number of people I've seen who are frustrated by constant popups, reminders and so on far outweighs the number of people who I've encountered talking about how much they want to sign into multiple accounts…
