I think you're missing some perspective on this; a small % of activists on the left (mostly on college campuses) do not represent the trends of liberals in the USA. I can't think of a mainstream Democrat who considers these serious causes (including liberal ones like Bernie Sanders or Elizabeth Warren).
The reality is the left has been making huge inroads on social causes in the last eight years - in fact, this may be the primary enduring legacy of the Obama years. The public perception of gay marriage, police violence against blacks, and marijuana use have all drastically shifted and led to very real changes that won't be undone. I wouldn't call this overplaying their hands.
Also, I wouldn't extrapolate much from this election. Obama is a fair bit more liberal than Hillary and is extremely popular compared to her.