I assume that the user that you are responding to was probably referring to Manchin, Sinema, and the various old school Democrats that engage in insider trading and the like and refuse to fix such issues in our laws.
In addition to the more extreme examples like Manchin and Sinema who exist as spoiler votes, the majority of the Democratic party also enable the Republican party by constant attempts to compromise resulting in a rightward Overton window shift. Because Democratic politicians refuse to confront Republicans when the latter refuse to engage in good faith arguments, agreements, and debates.
Outside of that, they also tend not use what power they have to do good. Like how Roe v Wade was never codified, even during times when Dems had control of the house and senate.