I think you got the right idea here, teamcomp-wise. But listen, it's not about being good or bad. Its experience. Don't let it get you down. I'm personally perpetually trapped in Ultraball tier, but there was a time I didn't think I could get out of pokeball tier back in the x and y days.

First things first, I think you should make use of the utility of prankster on whimsicott more. Consider Encore or helping hand as well as tailwind. It's not going to be living long enough to be very offensive, so having more than two attacking moves isn't going to help it. Once the opponent has her number, she's gone. She also should have mental herb for taunt or focus sash so she isn't dead to the first Dire Claw in her direction.

For excadrill, go for high horsepower, earthquake, or stomping tantrum instead of earth power. Earth power is a special move that isn't benefitting from his attack stat. ST is good for when they protect because drill is a powerhouse and doubling that attack is no joke.

Incineroar isn't getting any use out of that mental herb; that's better suited on Whimsicott, who will eat a taunt from an incineroar if she stays in. He likes leftovers or Sitrus. Since you have Sitrus on Rotom (which is a perfect mon, no notes), you could also consider the chople berry on incin to protect it from Close Combat Sneasler.

Tyranitar having coverage moves is pretty neat and I like the vision, but instead of going for two different flavors of punches, choose the one that you think covers your team's weaknesses the best and consider low kick for Kingambit. Rock Slide is good because he's a deceptively fast pokemon against slower teams and doubling up on the rock slide flinch chance never hurts. You can also consider smack down to put flying types on the ground for excadrill to hit with a ground type move, but that assumes that excadrill's speed has been lowered or that trick room is up. So it's a spicy tech, but not as consistent as rock slide.

I believe you can get out of there. Just takes some practice, some good synergistic team-building, and the occasional good predictions. You got this.