Did anyone else think this was just plain terrible?

yes. I am 26 and saw this in theaters and again on redbox bluray when it was available just to double check. I fell asleep both times. I have only done that two other times at the movies, Nightmare On Elm Street 2009 and Underworld Awakening.
very disappointing because I love Hawaii, George Clooney, and Alexander Payne.

The characters were inconsistent and deeply flawed but perhaps that was intended by the screenwriter. The impact of the wife's affair and the connection of her lover to the sale of the property worked well. Matt changed as a result and finally did the right thing by not signing the pristine land over to a developer. That scene when his conscience kicks in and as trustee he refuses to sign the contract is actually the climax of the film, not the scene in the hospital. Hopefully someone soon after told him about "The Nature Conservancy" and he was able to make a deal with them.

From the OP;

"I think this is easily the worst movie I've seen this year"

There are some movies released in 2011 which I thought were worse. For instance; "Apollo 18", "Green Lantern", "Captain America: The First Avenger" and "Conan the Barbarian".
But there was a lot I didn't like about "The Descendants".
I rated it 5/10.

"-The plot was overflowing with cliches"

That's true of almost all movies. The question is, what cliches does a person like or dislike?

I disliked these cliches in the movie;
- The 'overwhelming' problems of entitled First World white people.
Clooney, very rich lawyer, is married but didn't have time for his wife until she got her skull crushed.
Clooney is a dad but didn't have time to see his kids until his wife got hurt and is angry because kids can have problems!
The rich cousins don't work and they are upset that they are running out of money!
I did not care about any of that.
- Family members are screwed up but just by getting together in a time of sadness everyone makes a complete turn around!
Clooney can't be touched and doesn't like it when other people who touch. (Was he a high functioning autistic?)
By the end he's holding, hugging and kissing.
Youngest daughter is a foul mouthed texter but by the end she's polite to everyone.
Older daughter is even more foul mouthed. She's drunk at school, hates her mom and dad. At the end she's completely matured.
The oldest daughter has a druggie friend, Sid, who starts out as a jerk but it's OK. His dad just died! And then he's a polite nice guy.
These character arcs are predictable and frankly forgettable imo.

* Still, I gave the movie 5/10 so I must have liked some things about it.
- The developer land grab in Hawaii. Best part of the story. I wish that had been the focus of the movie with more acting moments with Native Hawaiians, about their hardships and more of an exploration of their lives.
- The scenery. I've been to a couple of the Hawaiian islands. They're beautiful and I often ignored the silly story to focus on the wonderful backgrounds.
- The music. I like Hawaiian music a lot. The soundtrack was a joy to listen to.

BB ;-)

it is just in my opinion - imo - 🌈

Yes this movie is atrocious. Saw it in theaters, literally fell asleep. This was only one of two movies I've ever fell asleep to - this, and Underworld: Awakening.
Then when I rented it at redbox much later, I fell asleep again. WTF!

This movie is TOTAL *beep* And I love Alexander Payne's movies and most all of George Clooney's stuff, especially his slower introspective movies like The American, Good Night and Good Luck, and Michael Clayton.

Have you furthered your education since this cry for enlightenment, I wonder.