I have mixed feelings about it.
One of the things that I've always loved about GoT is that the story it's been telling has been different from the story of the "good guys" being put in peril and then pulling through with some last second heroics like we get from pretty much every other blockbuster out there. I walked into the episode not knowing if the "good guys" would be able to pull it off or not, and I was legitimately worried for them for the entire battle.
The final 3 episodes could have been the white walkers marching south to destroy Kings Landing after taking Winterfell and it would have been great television, and telling a different story than most TV/movies. Or that idea that someone posted about the Night's King going to King's Landing first, and the living winning the battle of winterfell that way.
And also, yeah, we're not going to get history on the Night's King now, which is disappointing. We'll probably never get an explanation for what the symbol he keeps leaving means. Or why he keeps giving John ominous looks across the battlefield rather than just killing him. Because now they he's dead, they have to deal with the Cersei problem after sustaining massive losses.
I really liked how I didn't know what was going to happen, so I was legitimately scared for everyone on the show. It was an emotional, exhausting episode, and I was literally in tears by the end of it. But I don't like how the final narrative was basically the same as every other blockbuster out there.
Stealing victory from the jaws of defeat has been done to death. I had hoped that Game of Thrones would do something different somehow. And it didn't really.