Optimism really matters, and the fact that it all ends so abruptly is a real gutpunch.
I haven't seen the main endings yet, I only looked up Karlach's romance ending since I won't be seeing it for myself - but on general principles, I agree. For me, a good ending is one where I can imagine my character and possibly one or the other companion, depending on how their personal stories end, being involved in future stories. It is usually enough for me if the ending does not preclude that, but a little hint that life goes on would indeed be very welcome and add a lot to my appreciation of the story.
