Well, I don't hate Spirit Folk and Fair Haven per se, but in my eyes, they're just fluff. They add nothing substantial to the Voyager narrative. We already know that they often run the same holoprograms to relax a bit, that Janeway is alone and that holograms can apparently become sentient, after all.
As for Kes dying, I don't think it would have been necessary to address, because at the point in time when the Voyager finale took place, she probably would have had about a year left.
I'm not necessarily against giving her a normal life span close to the very end of the series, but I think the risk of it feeling much like an artificially sweetened and forced ending would be fairly high. I probably would have less qualms with it if that were to happen at some point in the middle of the series.
I totally agree with your comments here.
When it comes to Spirit Folk and Fair Haven, I don't hate them either. I just find them........well, unnecessary. As you wrote, they added nothing to the Voyager story. The same for the season 3 Real Life (which I constantly miss-write as Still Life which is an Iron Maiden song with the chorus Nightmaaaaaaares

However, how bland those episodes might be, they aren't insulting, like that episode who I think everyone knows about.
As for a prolonged Kes lifespan, it should have been done in season 2, 3 or 4, (or why not in the beginning of season 7
