Liking Pelosi or not isn't the point. It's the fantasy that Republicans will stop attacking Democrats if Pelosi out the way.
They won't stop attacking once she's replaced, but it would take years for whoever replaces her to become as unpopular as she is now, and so it would be a net electoral benefit to the Dems during that period of the next few years. Then, once her successor becomes as unpopular as she is now, they can dump him/her and pick another fresh face.
The issie would be whether there is risk in getting someone unproven but not demonized as much a chance. I think 10 as ML and 4 as speaker is long enough.
Perez has already done loads better than anyone since Dean. Couldn't have known that if DWS kept staying on and on, and considering she literally only got booted when it became more expedient for Clinton, who knows how long she'd have stayed had the primaries been different.