The digital remastering was not done totally. There would be new scenes added in with wonderful new animation. Just as you're happy and marvelling at the animation they cut to the scenes lifted 100% from the series, which while they might have been remastered look very dated. The switch between the "new" and "old" scenes is very jarring and affected my enjoyment of these movies.
That being said, some new scenes added in were very good and helped with character development. They also cut out a lot of fluff which made the movie much more enjoyable than the series, which tended to move along at a snail's pace.
Overall the first movie is leaps and bounds more enjoyable than the series as the pacing, animation (spotty) and character development are much better. The only drawback is the backstories of supporting characters mostly got edited out to make this a manageable length, but overall it was a good tradeoff.
