Could it be that, until recently, they were both minority leaders in the Congress, and could only get anything useful done if they could peel off Republicans to vote alongside the Democrats?
Pelosi’s now the House Speaker, and Democrats have a majority in the House, which is good, but they have barely gotten started. And the Democrats are still in the minority in the Senate, which places serious limitations on what they can’t achieve.
So again, tl; dr: It’s not that they’re weak or stupid, and it’s not that they’re corrupt; it’s that the composition of the House and the Senate matters an awful lot, and until the Democrats have majorities in both chambers (or the Republicans return to sanity), their ability to get things done has some stark limits.