I never minded the clothing thing. I file that under acceptable break from reality. Though if they wore tight suits when in action, it would have been better. Then you have to wonder if they would have allowed Cassie and Rachel to be in skin tight attire.
morphing in clothes was an acceptable break from reality. marco not being able to morph the security guard because the watch was constricting his arm was not.
visser three saying "it was foolish of you to come in human morphs" while in human morph himself. when he had rachel captured he said "aw is my form disturbing to you" and then morphing to human... i get the whole budget thing, but the way they worked it into the plot was horrible. i mean, visser 3 is chasing after the animorphs, comes to a locked door, demorphs to andalite, tailblades through it, and the remorphs to human before coming out!
the biggest thing to piss me off however was the yeerks that didnt need kandrona. through the series, they are able to rely on waiting 3 days to test if someone is a controller. even if they destroyed all those yeerks, the possibility of them breeding more would make the 3 day test impossible, which would have been a pretty big problem if the series had progressed.
i didnt mint the different battle morphs so much, lions are a lot easier to train than bears, but cassies was a horse? really?
the andalite disk, which was keyed to "a relative of elfangor's DNA" was able to change tobias from hawk to human. it looked pretty simple too, weird how ax wouldnt know that andalites have such a technology. also, it made no sense that it could only be used once, whereas when the elimmist did, it was an obvious one time favor.