I think saying “socially liberal” is probably fine still. Most people will think that means pro-civil-liberties. It’s just when you use one term to refer to every political stance when things become an issue. If you’re liberal, what in particular are you liberal about? That’s when it becomes more useful to break things into smaller pieces. Conservative and liberal are far too broad. Progressive/leftist is more exclusive, and you could go further to say communist, socialist, anarchist, etc. It’s pretty much impossible to wrap every aspect of your belief into one word with only about two choices for that word (three if you include the absence of either).