Liberalism, by definition, is a set of values that maintains that all social and political problems can be addressed via existing power structures and systems.
The current democratic party is about as liberal as they come, with many bordering on neo-liberal, which is just a new way to say “old fashioned republican.”
They may look neutered and impotent and terrible at planning, but they’re right where they want to be. They maintain power but can also use the excuse of not being able to get past Republican obstructionism so that’s why they haven’t pushed major political reform.
The system is only broken for those it’s not benefitting directly.
(You don’t have to like them, but you need to vote for them right now because I rather have a grifters in charge than evil grifters who want to bring about the dark-ages all over again.)