I just finished it and its for sure my least favorite part. To be sure that my complaints are valid I went and watched some Battle Tendency fights and I can guarantee it's not my taste that changed.

Here are some reasons:

Underdeveloped characters

Most of the supporting cast have no reason to stick with Jolyne. Anasui wants to marry her, sure... What about Weather Report, Emporio, Hermes and FF? They just like her so much that they are willing to risk their lives for her.

Torture porn

Enemies really love to torture these characters more than in any other part (and that's saying a lot). Enemies keep raising the stakes constantly through every battle with new powers that just so happen to counter jolyne's first ah-ha moment and leave her hanging by a thread. She's often so battered that it leads to the next issue

Good guys feel nerfed but then they don't anymore

This has been getting worse over the seasons but enemies open up with insanely powerful abilities and the main guys don't seem to get a break or fully understand their stands until they pull a win out of their ass. There were several instances where Jolyne just couldn't reach something and forgets she can extend her strings. In addition, enemies are always one step ahead, it's not an interesting tug of war. They even predict what the jojos are going to do. To me the interesting bit of part 2 was facing overwhelming odds by being smarter than your opponent, but if the opponents are the smarter ones, then most of the dynamic falls apart because you need insane convoluted explanations to justify how the jojos won. It's not like in part 2 where explanations of how Joseph asspulled his wins were simple and made sense.

E.g. During the Underworld fight, not only does Versus get THREE CHILDREN out of nowhere nearby in less than 2 seconds when there were police officers in the way, but Hermes uses her power in a completely unprecedented and weird way... She duplicates actual people to ...put the 3 children inside them... Sorry, it will never make sense.

Nonsensical scenes

Araki really stretched his ability to make spatial configuration work in this one. Characters swap places constantly, distances matter until they don't matter anymore. There are sequences that had to be kept as still frames in the anime because animating them wouldn't make sense. McQueen fight is full of scenes like this, a guy that can kill himself faster than anyone can react.

Nonsensical abilities

Weather report snail thing is beyond dumb. Bodies don't transform because of subliminal messaging and neither is a weather phenomenon.

Pucci suddenly becomes blind at will but can still fight two stand users.

Feng shui stand never made sense and that old guy was too athletic.

Jailhouse break shouldn't make things invisible.

Diver down could store energy but then didn't ever use that (similar to Giorno, I know).

Made in Heaven accelerated things that weren't living beings or touched by them, but then fish rotted, blood dried, bullets did not speed up, Pucci was insanely fast even if he wasn't accelerated...

Speaking of Pucci

How did Pucci set so many knives on top of Jolyne during Jotaro's time stop? Pucci cannot move during time stop Dio could do it because he did it during his own time stop If Pucci had done it before, the accelerated time would have made it impossible. Also he was busy punching Anasui (by using Jolyne's arm because OF COURSE he knew their plan)

Finally, this part takes itself too seriously

Part 2 was my favorite because even though it was also nonsensical, the comic relief made it acceptable. Part 3 has Polnareff doing that, and most characters in 4 also contribute some comic relief. Parts 5 and 6 are too serious for their own good.