Is it though? It ended up badly for everyone who did it
I think so. It's not like it was framed in the narrative to be a negative thing for the most part.
It may be something that other characters admire, to go off and adventure and leave your kid behind, but the repercussions are always there and usually bad[/QUOTE]
I disagree with most of those examples since it isn't something we are shown to that actually bothers other characters. Usopp's mom dies, but he never criticizes it. Franky ended up okay, so it's not shown he's upset about it. You might take things to be intuitively awful things to do, but Luffy genuinely doesn't care that his grandfather threw him off cliffs and Usopp outright venerates his father for abandoning him, so it's perfectly plausible to say that they're genuinely not bothered by parental abandonment even if some hardships came with it. I don't deny there are some bad consequences, but if the characters don't care, then they aren't really meaningful.
Meanwhile, everyone who HAS parents is well off
This one is pretty debatable. Sabo had parents, look how happy he was. And you can't deny that Doflamingo's life was ruined by his father, and then drastically improved once he shot him in the head. And Sanji probably left the family for a pretty big reason.
Besides, if you're including adoptive parents in your previous list, then most characters did have parents. Luffy had Dadan and mikoto, Zoro had Kuina's father, Nami had Bellevere, etc. But that works conversely too. Law had both Doflamingo and Corazon as father figures, and he had a mixed bag right there.
And how do you even qualify Helmeppo. He lived a comfortable life, but was not a happy person until he removed his father from his life and joined the marines with Coby. Was his father then a positive or negative influence?
There are definitely good parents in OP that take care of their children, and you could argue that the adoptive parents picked up the slack where the real parents left off, but as far as I can see, parental abandonment doesn't seem to be a real issue. It either works itself out by having someone else come along or else the person in question just doesn't care.