DNC have not had more than 48 senate seats in 13 years. When they did have 58 senators in 2010, for less than 2 months of congress in session, they caucused with 2 independents to have supermajority to pass the Affordable Care Act which gave free healthcare to over 50 Million americans and made healthcare more affordable to a comparable number of people, they would have passed that Public Option healthcare plan if not for Independent Senator Joe Leiberman refusing.
They also banned PACs in 2003, something they were attempting since 1995, and it lasted until 2007-2010 at which point the SCOTUS deemed it unconstitutional in the Citizens United ruling.
As far as banning discriminattion, protecting the environment, antimonopoly enforcement, and taxing the rich: there are examples of all of those things from every single DNC presidency and congress.