This is a spoiler-free review from the perspective of a fan of the visual novel who read EX routes in the VN before watching (Thank god).

The Ex routes in Little Busters are three additional routes unlocked after completing Refrain. In my opinion, they feature some of the best stories in Little Busters, but unfortunately, this anime adaptation of 2 of them is awful.

Saya:
Saya's route in the VN is one of my favourite works from Maeda, despite its quirks. However, this route is already, from the get-go, very difficult to adapt arc because of how it's structured into the VN. But that still doesn't forgive the poor, low quality adaptation that we're offered.
The anime adaptation for this route has major pacing issues because of its time constraints. While yes, it does follow the story, it rushes through it very fast, not giving time to develop Riki and Saya's feelings, resulting in their relationship feeling too comical and overall flat. While a lot of people agree Saya's ending in the VN is one of the highlights of reading it, the anime feels like a rushed mess that makes very little sense. Giving so little time to try to figure out what's going on for yourself in the plot, to become familiar and attached to the characters, and this results in a very weird story that feels not thoroughly thought out. It's not the worst adaptation in the world, but it's bad enough that I would rather you not watch it than only watch it over reading the VN.

I do want to mention some positives though, it does reference some CGs use the same soundtrack, including the infamous ED. I also much prefer Yui Horie's voice for Riki.

Sasami:
Thankfully, ironically, albeit sandwiched between 2 awful adaptations, Sasami's arc is probably the best adapted route in the whole series (including S1 and Refrain). In the VN I found that this route went on a bit too long for what it was, but the anime gives the right amount of time for everything without leaving anything out. In fact, I even think it improved upon it by removing the weird sub-plot of Sasami suddenly loving Riki despite loving Kengo the entire rest of the series. The adaptation faithfully uses all the CGs and plays the story out faithfully, and it feels just as good as reading the VN. I can even recommend watching it over playing the route as it's significantly shorter, saving people time. Unlike every other arc/route in Little Busters, this is the only part I can confidently say that you wouldn't be missing out on anything (aside from the more charming art style, I suppose).

Kanata:
Unfortunately, the good ends there. Kanata's route in the VN is my personal favourite route (aside from Refrain, of course), and its treatment in the anime is quite frankly an abomination. Kanata's route is probably the deepest, darkest-toned story in the game and has way too much content to cover  within the time the anime offers, which ends up coming across as insensitive and unwatchable to VN readers. The anime does cover all the key scenes, but it's like a highlight reel, leaving out all the substance that makes this route so good and makes those scenes so impactful. Leaving an awful aftertaste to end the series on, unlike the VN which was the complete opposite.

To Finish:
I do like the new opening and ending sequences (using songs from the VN). The things this adaptation does carry over are good and fairly faithful. Like I said in my previous reviews, the art style loses the charm of the VN and the animation isn't anything to celebrate. I do think production quality is a bit better than Refrain, less weird editing and using more of the source materials CGs to go off was a welcome change. But the stories aren't given enough time at all; it ends up feeling insulting to fans of the VN and makes Little Busters look a lot worse than it actually is. Overall, I recommend watching Sasami's arc, as it's fun to see it faithfully animated, but for Saya and Kanata's, I'd rather you not watch them at all than choose to watch it over the VN

My Anime vs VN Ratings:
Saya route - anime: 3.5/10 VN: 9/10
Sasami route - anime: 7.5/10 VN: 7.5/10
Kanata route - anime: 2/10 VN: 8.5/10