I love the world building of the 2nd half, and would argue it doesn't need a clear ending. Your imagination gets to fill in the blanks.

While some other of his books do not have the most satisfying endings, Seveneves was the only one where it seemed like he simply gave up trying when writing the last 5%. Compared to the previous sections, the end just seemed like it had no effort put into it. Everything after the death of the doc just seemed abrupt and clumsy. It seemed jarring compared to how much care he seemed to put into the detail of the earlier passages.

I would argue the sci-fi indeed gets so hard, that it becomes soft again by nature. The technology falls away from the focus, as it should, but it is still very much there.

I think it's pretty clear from the comments here that there are those of us who just can't really buy the jump-cut and there are those who can.

I was listening to it on audio book and after the "5000 years later" I paused it and didn't pick it back up for a long while. Slogged through the rest. Won't read/listen to it again. The ending was ok. This was my first Stephenson book. Not going to do more.

I agree with you, you are not alone. Seveneves had some great ideas, but he spent way too much time on the science and put almost nothing into character development. The characters were so flat, the interactions and motivations were lacking, and ultimately I just didn't care about any of them. I can't recall a single character from Seveneves but while I can't remember all their names I very much do remember the characters from Snow Crash.