It's literally based on the fact she has experience in creating an entire executive agency from the ground up that has a budget in the hundreds of millions and 1000+ staff, and Bernie...does not.
That Emily Tisch shythead arguing supporting Bernie over Warren is intrinsically sexist is garbage, but attempting to downplay Liz's achievements by arguing they're equivalent to being Mayor of Burlington does seem sexist, if not just plain idiotic. The correct pro-Bernie argument here is that moral vision and courage is more important than intelligence, not that Liz and Bernie are of equal intelligence or executive experience. She's clearly the most intelligent candidate in the race. But Mayor Pete is probably second, which shows you how intelligence is not the be all end all of evaluating who is fit to be President. Biden has just as much executive experience, if not more, than Liz, but he's totally unfit to hold the office, which shows you that executive experience is not the be all end all. Bernie would be better suited sticking to his strong suits (morality, consistency, abilities to inspire and activate, foreign policy, etc) than making up arguments about how he's just as good when it comes to executive experience or intelligence as other candidates.