They couldn't even end it on a plot twist that left the viewer surprised or wondering. Everything all wrapped up nice and tidy, all the outcomes pretty predictable, many things essentially full circle, lots of the lesser plot arcs just sort of left to fizzle out. But it wasn't a disaster or without enjoyment, just a bit of a tame way to go out.
In the context of the rest of Season 8, I guess the finale was OK. In the context of the whole long journey since the start, not so much. An underwhelming finish, which, ultimately, future students of film and screenwriting will use as evidence that you should never outpace or outgrow the original source material. I wonder how (indeed if) GRRM will meld this into his own concluding book.