Ya little whippersnappers don't have any patience. Back in my day, a final battle could go on for 100 chapters and we'd be no worse for wear. Why, I followed a manga where the final battle where the hero and the antagonist played 2 hands of mahjong went for 250 chapters, and with a monthly schedule, 20 real life years. Imagine how fast Jump would axe something like that.
Sukunawanking is going nuts, but Gege's been fair about not letting him just whip out a new move or form that absolutely turns the tides in his favor. Everything he's done so far has been an extension of whatever he could do, or something he observed someone doing. At the very least, Gege's been trying to push his magic system to its absolute limits using Sukuna as a foreman. What makes it frustrating for readers is probably how hopeless it feels for the heroes who have no unleashed anything groundbreaking, and how they're slowly chipping away at him like a squirrel biting into an acorn. It's... a strange choice.
That's what I'm saying! The direction taken for the Shinjuku arc just seems to lack finality. Oh yes, we know that Sukuna's gonna unleash the... Instrumentality plan if he wins just for shits and giggles, but goddamn does it feel like everyone's just fighting just because. At no point do you read this arc and feel like, "Oh boy, we're in the endgame now!" It just feels like watching a football manga but they kick each other instead of balls.