It's a fair complaint but they tried deprecating % and that ... well ... ended badly.

Yep, can't please everyone. Someone is going to complain that you broke backwards compatibility if you remove something, and someone is going to complain that you've muddied up the language if you don't. Python 3 was an attempt to straddle that chasm and it definitely caused problems.

I think you just have to play it by ear. Old formatting styles seem like one of those things you want to leave alone for a really long time, because they're so common that it'd be a major PITA to fix all occurrences, and because it doesn't seem like there's an obvious negative ramification to allowing the old styles to continue to evaluate according to the old methods.

It is built right on top of .format(), so perhaps it's more accurate to say 3.1 ways.