The difference is that at local levels Democrats often have to give into progressive demands to maintain coalition government, but if you let them out of sight for even a minute they will immediately start in on full-scale gentrification projects, breaking up and pushing vulnerable communities right into Republican controlled areas or sell your water rights to corporations.

Edit: Outside of local level stuff it is really really hard to pressure Democrats to do anything because they have all the media and elite donor contacts to literally warp reality in such a way to make in nearly impossible to effectively communicate a broad-spectrum agenda. The Squad was able to do some stuff because they are great rage-bait, but they are far too geographically scattered and disinclined (because in the end they are Democrats) to actually organize a proper independent party resistance to the democratic party machine.

2nd Edit: Also, moving up in the Democratic party is not based on your ability to ‘work with progressives’. In fact, this is seen as a weakness and ‘giving into radical elements’. What is laudable to the upper echelon is getting large donors and working across the aisle with ‘moderate’ Republicans. Anybody who is up to at least state-level knows and understands that if they want to move forward, they have to work around the progressives, not with the progressives. This involves a lot of promise making, but never actually delivering or working to deliver on those promises, unless it is ok’d from above as a strategic measure.