Several thoughts from me on all this:
I was 25 when I discovered the Harry Potter novels, shortly after I was married in 2000. My wife and I eagerly devoured the four books that were available at that point and became instant fans of the series. In fact, we feel as though we had a second childhood in the early 21st Century for all sorts of pop culture related reasons (The Lord of the Rings films, the admittedly disappointing second Star Wars trilogy, and the return of Doctor Who in 2005, absent from UK screens since 1989), and the Harry Potter novels were a key part of that.
Sadly, I don't think the films are as good as the novels for several reasons. Some elements of them are good (and John Williams's contribution is absolutely outstanding, as you rightly point out), but I confess I was surprised at the lack of show-don't-tell in the first film. It ought to have opened with Voldemort's murder of Harry's parents. That should have been the very first scene. I also wish the films had been helmed by a genuine cinematic maverick like Peter Jackson or Guillermo Del Toro or Terry Gilliam to transform great novels into great cinema (the arguable exception here is the third film, which was directed by Alfonso Cuaron). The screenplays for the most part were too timidly faithful to the source, and often skimmed over important elements. For example, the Mirror of Erised is a vital chapter in the first novel, but we get no sense in the film of Harry slowly becoming obsessed and losing himself. This ought to have been dwelt on in the film and directed with a lot more artistic flair. I'm also not a huge fan of the casting. The supporting cast are terrific (Alan Rickman, who ought to have been in the films a lot more, for instance) but of the central trio, I only really rate Rupert Grint. I've never been a huge fan of Emma Watson or Daniel Radcliffe.
All that said, I can fully understand why for some people (including you) these are beloved films with massive nostalgia value. They have massive nostalgia value for me too - especially the first two, which I'd argue aren't as good as the later films. For me, the only film that really hits the nail on the head is the last one, though I still think Voldemort ought to have looked scarier - where are the red eyes? - and probably ought to have been a motion capture performance.
On the subject of nostalgia, I think it is possible to recognise shortcomings in a film from an objective perspective whilst it still means a great deal to one personally. For instance, The Goonies is a massively important film for me for very personal reasons, to do with the memory of my father taking me to the cinema to see it when it was released (I was ten). At the same time, I think The Goonies is actually a pretty loud and obnoxious film in a lot of ways, and it certainly degenerates into pantomime in the final act. In contrast, Back to the Future - a film I saw with my father at the cinema around the same period - is a film both wrapped in nostalgia and a film I consider objectively great.
On another note, as a Jewish person (by descent via my maternal grandmother), I don't see anti-Semitism in the Harry Potter films, nor do I find them offensive in any way. People read all kinds of paranoid things into pop culture these days, but I think reading intentional anti-Semitism into the goblins is foolish at best and deliberate shit-stirring at worst. I also get immensely irritated by self-appointed activist types who claim to speak for all Jewish people by saying this, that, or the other is offensive to Jewish people, as though we were a homogenous, Borg-like collective consciousness. But that's an axe-grind for another day. Personally, I don't do "offended".
Which brings me to my next point: I think the house elf oppression thing isn't intended to introduce slavery as a major theme of the novels. It is only really introduced as a means of Rowling poking fun at her younger, activisty self (Hermione is clearly Rowling as a teenager, I think). I think that whole SPEW business is intended to simultaneously sympathise with a certain idealistic mindset and as a means of pointing out certain issues that appear black and white to teenagers often have shades of grey, where both extremism and apathy are foolish positions to take. I actually think on a metaphorical level, this rather minor subplot works quite well, and certainly could have been introduced in a lengthier dramatisation of the novels (perhaps the upcoming TV series will tackle this).
Finally, JK Rowling is a fantastic writer. I'm huge fan of both Harry Potter and her Strike series (check those out if you haven't already). As for her personal views, she is fully entitled to them. I'm a separate art from artist extremist. More on why in the two articles I've left links to below, if you're interested. :)
https://medium.com/framerated/curate-dont-cancel-e681b184d0fb
https://simondillon.medium.com/are-we-allowed-cancel-cultures-illusion-of-authority-d68ab8312711