One doesn’t wish to be unduly negative in a lighthearted thread, but the sad truth is that the above is at least as big a fantasy as Harry Potter. UK social services regularly fail to deal with much worse abuse than Harry ever suffered.
As Rowling knows - her excellent adult novel The Casual Vacancy is an unflinching look at how easy it is for neglected kids to fall through the cracks. But Potter is a kids’ fantasy, so it is unfair to criticise it for not engaging with the realities of mid-90s social care provision. It’s like asking why a chess player doesn’t just pick up the opponent’s king and put it in a checkmate position. Because that’s not the game, that’s why.
However, within the game of kids’ fantasy, it does become increasingly obvious that the wizarding world is riddled with bigotry, not just individual but structural and ideological. House-elf slavery is accepted by almost everyone, including moral mentors like Lupin and Dumbledore. Even beyond that, it’s clear that the treatment of other non-humans is also appalling - they are pushed to the margins, written out of history and when they push back against this treatment this is taken as evidence of how dangerous and uncivilised they are. The last two or three books actually do a pretty good job of showing Harry realising that it’s not a case of Voldemort and the Death Eaters as the only villains - there are deep-rooted problems in “good” wizarding society too.
And then he defeats Voldemort and… nothing else happens? In the final flash-forward chapter there’s no sense that anything else has changed, Harry is an Auror who, yes, is still hunting down Death Eaters but isn’t noticeably taking on any of the other problems he and we have noticed and there’s no sense that e.g. house-elves are now free, or other species’ rights are recognised etc.
So from the perspective of, say, house-elves the Wizarding War is just a question of which faction of the oppressor is going to have its boot on their neck, somewhat analogous to the import of the French Revolution for Haitian slaves. A glimmer of hope that things might be about to get better, followed by the cruel realisation that all these fine words about Equality, Liberty and Fraternity don’t extend to you.