Length is the most important thing, everything else is somewhat secondary. We should be shifting thinking of this to passphrases rather than passwords.

I’m sure most of us have seen the “correct horse battery staple” XKCD, but that’s what people really need to think of as passwords now, not my-favourite-celebrity-but-with-the-“e”-changed-to-“3”-and-an-exclamation-mark-at-the-end.