I think the animation was pretty cool (the drawings/designs), but I do wish the characters had more movement. But like every TOS episode and movie (besides TMP) it had to deal with budget limitations.
Not just budget but schedule. The first season of TAS was produced under an insanely tight deadline, so even by the standards of '70s limited animation, Filmation had to cut a lot of corners. This is most notable in the lackluster voice acting, which is often more just line reading than performing. The actors just went in to whatever studio was convenient to where they were, banged out the lines without any directorial guidance to speak of, and literally mailed in their performances.
The 6 episodes of the second season were produced at a more leisurely pace, and you can tell that the acting and animation are better on those.
Kinda unfair that TNG show/movies and all the other Trek shows got huge budgets to do pretty much whatever they wanted when TOS had to constantly cut corners...even in animated form!
Actually all of the Trek movies except the first and most recent ones have been shot on quite constrained budgets. And even the newest movie had a relatively tight budget, which is why they shot the engineering scenes in a Budweiser brewery rather than building a set. And the TNG-era shows and ENT didn't have budgets nearly as high as it appeared. They had to cut corners like every other show. But Rick Berman, whatever faults he may have had creatively, was very, very good at getting the most for his money and making the shows look more expensive than they were.