It's also the reason why WYLB is such a difficult episode to watch for a Niner like me. DS9 wasn't just a place, it was a time, and this episode reminds me that that time is over. We can rewatch it and enjoy the journey all over again, but there will never be more. I'm glad that DS9 ended on its own terms and that didn't it attempt to continue ad infinitum. But I'm also sad that it's over, and that bittersweet sentiment is something that What You Leave Behind captures very well. For all its problems, the episode hits the right emotional notes when it needs to, and it serves as a worthy finale to a brilliant yet flawed series.
I agree with this part especially. While the finale has some obvious flaws, I still find it extremely satisfying on an emotional level, and that is more important. It also brings everything to a close very nicely. There is a sense, obviously, that life will go on for these characters, but the saga has reached its end.
"Bittersweet" certainly describes the feeling. Odo returning to the link is perhaps the best single moment of this kind. But there are many good ones.