I don't think fluidity is really the best consideration for quality of animation when it comes to appreciation, especially in anime. Anime by nature of the industry and the culture over the decades relies on more limited and and by definition less fluid animation compared to western animation principles.
With regards to logical transitions and good physics, I agree this is far more important. But I think I can express it in a more general way that applies to all art styles. The importance isn't how realistic something is, because animation tends to explore the more fantastical. So when it comes to animation transitions and properties of physics, we don't necessarily want to compare it to the ones in reality. But it is very important to convey the feeling that the animator does understand how these properties work, before they take advantage of it create something outside of natural rules.
So what we can look for is
elements of reality applied in things which might have no grounding in reality, if the scene calls for it. If two superhuman dudes are brawling it out in the sky and they are flying around with the aid of powers or whatever and blasting beams while swinging swords, the important part is not "damn, this makes no sense how are they even defying gravity?" because that's honestly a stupid question and doesn't matter.
What would matter would be the nuances in the movement and seeing how the animator has chosen to convey the subjects defying gravity and what impact this has on the momentum of their movements. When they use energy blasts, is there a satisfying sense of feedback to show the strength of the blast? As their swords clash does it feel like there is real impact and strength behind the motions? All the little things make the animation feel more exciting and add weight to the movement of characters.
Another interesting form of fantastical animation is morphing. Look at this example:
https://sakugabooru.com/post/show/4625
There is zero basis in reality in terms of whatever that thing is transforming into a person. We don't know what properties the matter has and why it behaves the way it does. But yet it looks great because it shows a great understanding of human anatomy and how things "feel". Every little subtle movement as part of the transformation looks like a person breaking out of some weird gooey shell of sorts.
But I don't think any of this really answers the question you want to ask which is "what is bad animation and why is some things which look bad to me considered really good to other people" and this is where I'm going to point something out: Animation is art, and as such art is in the eyes of the beholder. When it comes to technical elements, as long as there is a good amount of talent and effort shown, it's not "objectively bad" animation. Most animation isn't. The ones which are objectively bad are incomplete animation or just bad looking stuff which was clearly rushed and pretty much everyone will agree. When it comes to people arguing over whether stylized types of animation are "good" or "bad" it is very subjective, and even the people who love it should recognize that there is no objective truth. The purpose of art is to express yourself and to also communicate something to an audience. If someone doesn't like what is communicated, that is also a fair response.