There is a LOT of specific procedural knowledge and gamesmanship that goes into being the House or Senate leader. Look at how effective Pelosi and Reid were because the played the game and knew the loopholes. Same with McConnell for the Republicans (look how he handled the Garland/Gorsuch issue). Remember Tip O'Neill and Newt Gingrich?
They were all well versed.
Conversely, Paul Ryan - very smart, but not ready to be a leader, and it showed with the House healthcare roll out. He is coming along, but his inexperience is costly.
This is the Democrat's conundrum. They will lose that valuable experience if they ax Pelosi, and I suspect that she has purposefully made herself indispensable by not bringing along any potential future replacement. Further, that experience is especially critical for them since they are in the minority, and they have to rely on knowledge of the rules more than ever to "resist".
It is a win/win for the GOP. Personally, If i were the Dems, I would cut bait with Pelosi and take my lumps because she is so toxic. I hope they don't, but it's going to be a long several years for them either way.