To get at the parts that I do, obviously. Which you already know since, like you said, we've done this song and dance many times before. The ratio of stuff I like vs I don't is low, but enough for me to keep going.
You might think it's not worth it, and if this were the only manga available for me to read, I'd probably be inclined to agree with you. But I'm reading My Hero Academia and now The Promised Neverland, both of which satisfy me very much along with this. Consuming two manga I like a lot takes the bad taste that OP may leave out of my mouth, so it's not a big deal for me to tolerate (even if I complain about it) to get to the good parts.
Besides, I actually like this arc...atleast relative to the other arcs. Big Mom has delivered thus far, I like the intellectual emphasis of this storyline, making fun of Sanji's L's and celebrating Pudding being a queen bitch has been a lot of fun, I am actually liking the design of a lot of the characters here...the only thing that's really underdelivered is the vinsmoke storyline. They're just so one note and stupid and feel like they primarily exist to show how Sanji is a shining beacon of goodness. And of course I have criticisms like Pudding's bond villain stupidity thing going on. But I have more positive things to say about this arc than most others. And I'm doing it while still having no empathy for the victim in question (Sanji). I doubt that's the case with you or others, but it's what I get out of the arc.
See?! I'm not the only crazy person who does this to themselves. And everything I hear tells me fairy tale is worse than OP. OP at least has some redeeming value. I've never heard anything good about FT that wasn't from DTL's mouth of madness.