If you're asking for opinions, I can offer one. Though I'm not sure you'll care for it. Certainly regardless of mine, you're not the only person who likes the episode. If you enjoy it more power to you. Since you're asking for enlightenment as to why some don't? Well I'll bite, here we go...
It started off strong with a good teaser. In fact the first time I watched it with the reunion scenes at the beginning I was stoked because finally they were going outside the box and doing something creative. I thought it was going to be a flashback episode in a way both showing how they got home, perhaps a few more adventures along the way, and where they all ended up in life.
Instead... no. We just got yet another time travel episode and Borg episode all thrown in one. Like some sort of dead horse beating special, two for the price of one. It's like the writers just got together and went around the table brainstorming about the most facepalming things they could do.
So you have future Janeway willing to change the timeline. Well that might almost make some sense except for why at that point? Why not a few weeks earlier to save Carey? Why not stop them from getting stranded at all? Her original plan was -not- to destroy the transwarp hub after all, to just get them home. Though I guess you could argue that all she wanted to save Seven and she's more important than all the other people on Voyager who died. Though that doesn't make our heroine exactly look good.
Then the Borg... well let's just take away any menacing presence they once had at all. Seriously, the way Voyager was invincible with it's batmobile armor and gunning down Borg Cubes with one shot, I've seen more plausible scenarios involving godmode on video games. Which essentially this is what it was, but if that's not enough they have to technobabble destroy the whole Collective's super technobabble transwarp whatever that conveniently leads all the way to Earth. Boy that would've been useful for the Borg in Best of Both Worlds or First Contact.
As I said, I liked the future part at first, but once it came apparent it was just a plot device to get future Janeway to the past with godmode gear, it lost any dramatic effect. Barclay's cured? So what... Tuvok got Vulcan Alzhemiers? Oh well. Chakotay's dead? Too bad. Seven? Well we'll fix that too and remove any drama while we're at it. If you're going to handwave away these dramatic moments and consequences... you lose the drama and meaning in even putting them on screen too.
The visual effects were nice, but I've said many times they enhance an episode, they don't define it. If you sprinkle sugar on crap... it's still crap. Wrap the whole package in a bowtie with absolutely no resolution beyond a single line saying they're home and a two second shot of them flying towards Earth while the end credits pop up and you end the series on a rather disappointing note.
Though at least it wasn't These Are the Voyages...