Yeah. I had the same reaction. I honestly think this is one of the greate 2/3rds of a movie of all time. But, it irks me that it only feels like 2/3rds of 1 movie rather than the 1st part to a 2 parter. I can get over it though and it doesn't ruin the movie for me, just makes it much worse than it could've been. Technically Gwen's subplot sort of got closure, but Miles was too much of a focus for it to feel like a satisfying mini arc to close on, especially when they still left the cliff hanger on Miles (and I loved Gwen's arc). Felt like the second to last episode in a TV series rather than a movie like that.

That said, it is my headcanon that they had to do this in negotiation with the studio to keep from making the Spiderverse into another cinematic universe or something. They already had the plot and story written, but had to split it into two parts because of Sony and this was the best point for them to do so while still having enough to work with for a third movie. I don't have any real basis for this, but it makes sense to me.