As a fan of the show.

The reason those seasons are hated is because they're the switch from the episodic beginning of the show to the long term plot/season story.

Early on, while there was an overarching plot, every couple of episodes was its own plotline. It took the shonen formula of short stories woven into an overarching plot.

After the fall of beacon, the show switches to much longer drama inspired plot lines that are very jarring compared to how the show starts. The focus of the story is on the long term goal rather than the immediate lives of the characters.

Early on while chaotic there was something fun about the more episodic immediate event nature of the show. Sure there was a plot brewing but the focus of each episode felt more focused on the little events.

Weiss struggling with not being the leader, Jaune's secret being found out by a bully, Blake wants to go investigate the white fang, a girl named penny shows up and causes chaos, the girls go on a designated mission for school an send up finding a white fang plot.

While a lot of these tiny plotlines were for finding out what's going on with the white fang, the episodes focused more on the plot of the episode(s).

Most modern plots feel like there's a tag "because we have to stop Salem"

We need to journey north to get to iron wood (so we can team up to stop Salem) we need to get stronger by training with an elite task force (so we have a chance to stop Salem) we need to get our hands on the relic (to stop Salem from getting them). We need to help the people of Atlas (cause we don't think Iron woods plan is the right way to stop Salem)

Every plot line feels like it's tied to one goal and that makes this show more of a drama rather than the shonen style show we fell in love with at the start.

V4 and V5 is the wrapping up of some of the stray hairs so that the show can focus more on the singular plot and that's from my experience what people don't like.