The animation in Volume/Season 4 is very different to in the first 3 seasons. In the first volumes, they used a program that is nicknamed Maya to make the character models and used another program called Poser for the rest of the animation. In Season 4, they totally switched over to Maya, which is seen as the superior program. To me the backgrounds look more anime-esque and detailed now and the characters also look anime-esque, as they are more 2d. However, I made a thread on reddit and interestingly a few respondents thought that the original style was more anime-esque. ( https://www.reddit.com/r/RWBY/comments/8jaoxr/does_anybody_else_prefer_the_character_models_in/ )
The fight scenes have had a definite dip due to the lead animator/fight choreographer not being present, but apparently it improves again somewhat in Season 5, although I'm not expecting it to reach peak levels. It's lucky that by the time the fight quality diminished I was already invested enough in the actual plot and characters. Qrow is a pretty cool addition to the show too.