There were plenty of things that the show did that went well. One of the bad things about adaptations, in general, is that they are too critically compared to their original source material (and rightfully so), but often times people focus entirely too much on the negative and miss out on the good things that were done well.
First off, I liked the writing changes. There, I said it. Say what you will, but there was absolutely nothing wrong with the way the show was written. The biggest problem that people have with the show is from the cause of the show not having a decent budget -- the wrong morphs, the lack of enough morphing or fight scenes, or good FX for aliens in general (resulting in Visser 3 and Ax ending up mostly in human morph) -- they were all the cause of not having a proper budget, but it was NOT related to bad writing. The writing simply adapted to what they couldn't afford to do.
The storylines spread for each episode worked well, and were properly paced and directed. All of the Animorphs were written in character as well. The actors for Jake, Rachel, Marco, Cassie, Tobias, and Ax, were all good also. I never understood the negativity towards them other than the fact that they were much older than in the books, or that they didn't look the way the fans imagined them. But most importantly, as I said above, I always felt that the writers did a consistently good job at adapting to what they could or couldn't physically do on the show. It probably was very hard to write for a sci-fi show that could barely afford to morph more than once for a weekly episode, but they pulled it off imo.
A few other things that I also liked on the show:
a) Elfangor's Disc. This plot was brilliant imo, and I can't believe that K.A didn't think of it herself. The fact that Elfangor's Hirac Delest is unlocked by Tobias' DNA (go back and notice that Tobias doesn't touch the disc once until it's unlocked) to reveal that Elfangor is his father was much better done than in the books, where Tobias simply finds out by a letter read by some lawyer. I also liked that, in the beginning, the disc had a sense of mystery around it where it could've potentially worked as a sort of guide to the Animorphs if the writers had chosen to go that route.
b) The music. I loved the music choices on the show. I really wish they had more of the original score released that they had playing in the background so I could listen to it.
c) The barn discussions. I know that most of the time they hung around in Cyberia, but I feel most fans overlook the many discussions they also had in the barn for certain episodes. Most of those scenes felt like they were right out of the books where they would discuss about what to do, or if something was morally right or wrong. I also liked the way the barn scenes were set up in general, where you would see Cassie working on her chores or tending to animals, where Tobias would be sitting up on the rafters, or where the others would be sitting on a bale of hay. They even had rare occasions where once and a while they would have Ax standing in the corner as his Andalite self.
d) The humor. Marco and Jake actually joked around like they should as best friends, and because of this, most of the Jake/Marco moments were the best whether they were funny or dramatic. Also, Ax as his crazy self as a human in general, especially around food, was hilarious (the actor, Paulo something was excellent at pulling this off). I felt that the writers did an awesome job of breaking up the episodes with moments of proper humor. It was what sold the characters believably as kids as they went about their missions. This was improved drastically in Season 2 when they got a better grasp at what they could and couldn't afford do on the show. Most of the episodes were more character driven and funnier because they realized this, and I think they were heading the show at the right direction at this point too, had the show continued on.
Really, even though it was nothing like the books, the Animorphs show was a fun show to watch regardless. I used to watch it every time it would be on, and I'm actually kinda sad that it was canceled by the poor treatment it was given, by both the network and the fans.
