Ah cool work dudio, great to see you improving! yeah the backgrounds are an important part of the video because it makes it pleasing to the eye and make audience watch longer. What you may need to do if you really want to get your background quality to improve, is make the videos alot slower and build the stage first and make it perfect, then do the fight animation last. another thing to look into, would be your camera movement. Sometimes rather than have the camera move super fast would be to have the camers move slower and pan slowly in and out, or left to right during the fights. kind of like a movie fight scene. It makes the animation seem more flowing if you get what i mean
Sometimes it happens - When we don't feel the magic in the creation. Not everything will always turn out good and how we want. The most important thing is the practice you get each time you make something and learn from mistakes and perfect the art. If you keep it up, you will succeed. If you follow the advice these guys have given you, you will get better and better.
One thing I will say, is about your text boxes - they seem kind of random and out of place and somewhat lack the artistic flair needed to really make the animation seem "professional" if you get what i mean.
The goal is to make the text box sequence seem like it is inside a real game, or part of the story sequence in the action game. An example would be to use sound, and have the box fade in, use colors and stylish clean text, and even the face of the characters inside the box too. Like this for example