qutebrowser's adblock could definitely be better, right now it's really only a host blacklist: https://github.com/qutebrowser/qutebrowser/issues/29

Password autofill is something I want to take care once there's a plugin API, but there are ways to make it work (the password_fill userscript, autotyping in KeePass*).

Referrer control unfortunately isn't possible with QtWebEngine's API for now...

Zotero won't be possible, but I guess that won't exist any longer with WebExtensions either?

And Greasemonkey support is on its way: https://github.com/qutebrowser/qutebrowser/pull/3040