The software (TVPaint or Harmony or Toonz or Flash/Adobe Animate) doesn't make the animation fluid or not fluid, it's the skill level of the animator + how much time was the animator allowed to spend on animating the scenes.

There seems to be some misconception that the software is responsible for the skillfulness of the animation. If it is, would it be possible to make animation this fluid in the latest version of Harmony ? Of course, but it still would've been nice if they actually used TVPaint instead of resorting to paper. It’s a mix of digital and hand-drawn, depending on the studio.' Pete and Alex: 'Toon Boom Harmony and good ol’-fashioned paper and pencil. 'What animation tools do you use to produce the animation?' In an interview with executive producer Pete Browngardt and supervising director Alex Kirwan, they were asked: (although some animators are working with pencil on paper for rough animation, which is then scanned into Harmony for clean-up and coloring). I have several friends who are working on these shorts and they told me they are using Toonboom Harmony for animation, clean-up, and coloring. Harmony's frame by frame is mainly vector based, so you don't get the same results with vector drawing as you do with raster drawings. My guess is that despite being colored in Harmony, the actual animation was done in TVPaint.

Toon boom studio 4