Well sure, the Democrats could kill the filibuster with a simply majority (if they could get 51 senators on board) but they filibuster a lot as well, to prevent some Republican legislation. So I can see why they're too pragmatic - or cowardly - to remove it. Not the best source/graph, but a source: https://fivethirtyeight.com/features/why-are-so-many-democrats-considering-ending-the-filibuster/

As for the parliamentarian: they haven't been removed in a while, and the one before that also served for a pretty long time...I think the Democrats (again, cowardly or pragmatically) are simply trying not to escalate and make the parliamentarian a puppet of the current simple majority. https://en.wikipedia.org/wiki/Parliamentarian_of_the_United_States_Senate

I'm all in favor of nuking the filibuster, mind you: which would make the whole budget reconciliation thing a moot point. but I can understand the desire for some in the party to retain it as a tool. Fat lot of good it's doing us now, of course.