Demon Slayer had a 20 chapter fight against the final boss too with similar complaints about it dragging especially with Muzan having a much worse moveset compared to the Upper Moons. Frieza fight was also long as hell IIRC. I think the Goku/Frieza fight alone was like 20 chapters or something and Frieza fought a gauntlet of people before Goku showed up. Kaido was also a raid boss who went against Luffy like 3 times, the Supernovas on the rooftop, the samurai, Yamato, etc.. and many complained it was dragging (at least I did lol). MHA final battle has been decently long although it's switched up the opponents quickly so I don't know if that would count
Edit: Just realized comment was about final battles only. In that case, KNY is the only one that was similar to JJK in that regard. There might have been others but I can't think of them off the top of my head
Man, that Frieza fight is absolutely legendarily amazing to this day. Perhaps after JJK ends, i will remember the epic Sukuna fight fondly too. Anyway, i don't get all the complains of Sukuna vs everyone fight. It is basically a call back of Heian era where a lot of people fight him.
Sukuna is a raid boss. Basically they send their biggest DPS first to chip him. Then throw more people to chip him further to his last HP. Will not make sense if Sukuna is only facing few people, considering he is basically the strongest ever in history. Now only time can tell if he is like a Final Fantasy final boss with a 3rd form. Btw, Frieze also have many forms right? Boy, i wonder how people felt reading that Frieze arc weekly back then.
"Frieze is NOT dead yet???"
"Piccolo got a power up and still vannot beat him??"
"Vegeta is dead, we are finished"
"What can Goku even do now???"
"Frieze transformed AGAIN??? ASSPULL!!"
"Super Saiyan comes out from nowhere, asspull!!"
"PlotFrieza vs AsspullGoku"