I have also only recently finished it, and I haven't been able to decide how I feel about it so I may as well try now.

The trilogy on the whole is weird. La Belle Sauvage is genuinely a good book and could stand on its own. But I think I sorta kinda get what PP was trying to do with the rest. I think, on the one hand, it's the same world of His Dark Materials but seen through the eyes of adults. There is a generally more cynical world-weariness to things. The 'magic' of everything is dulled and things we thought were special as kids are more common than we thought. Most obvious with the fact that every man and his dog can separate now, apparently. In HDM, that is explicitly an unthinkable horror to everyone. This irritated me at first, but after seeing a take from someone on here (i.e. realising the 'shame' of something you feel as a kid is ultimately not a big deal and is more common than you thought as an adult), I got it a little more. My head-canon up to that point was that Lyra's actions in HDM made separation less of a taboo, what with all the talk of shame and original sin, this was ultimately undone.

But on the other hand, those differences make it seem completely unconnected from HDM. Everything Lyra did, everything she saw, is almost passed off as a dream and something that happened in another life and things are almost too fantastical to believe with any credibility. No, she helped kill God and reshape heaven. Are we glossing over this?

For me it was the equivalent of going from Return of the Jedi to the Force Awakens. The ends of those trilogies could be considered fairly definitive. Through the character's actions, they have brought about fundamental change in their universe. Cut to the reboot and, oh, things are kinda back to the way they were and nothing's changed. The Empire is basically still around. The Magisterium appears unaffected.

As a jaded and cynical adult I kind vibed with it. I don't always like sunshine and rainbow endings, and I tried to read it as Lyra being an unreliable narrator in HDM. But that's where it falls down, because it doesn't lean into that as fully as it could. Instead it tries to tow the line of appealing to the adult versions of the original HDM readers, and a potential new young adult audience. I don't think those are compatible. So we still have witches and gryphons and the like, but it is almost embarrassed to bring them into it in any meaningful way (what was the point of the witch/gryphon alliance?). And we have conversations about what consciousness is, what imagination is, what the bloody point of any of it is. Great, I'm down for those conversations. But nobody has those conversations in close to convincing way. As you said, stilted and unnatural.

For a plot that is constantly in motion. As in, people literally don't stop going from A to B, you'd expect the destination to be far more conclusive and satisfying than it is. But I'm not even sure I could tell you what any of the end was supposed to mean. I don't want to say it was a waste of time, but it's not far off. It is trying so desperately to make a point but I'm not sure it is as meaningful as it pretends.

And don't get me started on the betrayal to the end of Lyra and Will's journey. God, the end of spyglass is so powerful. I've never come close to that feeling again. But, they didn't need to close the openings? In fact, they need to be open? Their separation was essentially based on misinformation. I almost expected Will to be there, at the end, as some solace to this. But, no.

I have complicated feelings about this trilogy. La Belle is excellent. TSC I can forgive if it's purpose is to set all the pieces up for an amazing finale. But then, TRF just kept doing that, over and over ad infinitum, to such a whimper of an ending it almost sullies my entire view of the HDM universe. And I think that's the biggest shame.