An adaptation completely botches the original theme and message

[u/Morr4Seiya]

Mulan(2020)-They give Mulan superpowers which is not only lame it goes against the message of the original about equality and struggle,plus they removes Shang because apparently having Mulan date her superior was "problematic" even though Shang genuienely respected Mulan and their rank was never brought up

I am Legend(2007)-You know why the story is called "I am legend"? SPOILER ALERT the protagonist is the actual monster,humanity is gone and the vampires have a actual society and the protagonist kills and terrorize them

Animal Farm(2026)-On the very slim chance that Andy Serkis ever sees this,here's the thing Andy,Animal Farm was not a children work it was not supposed to have a happy ending,you never heard of cautionary tales before?

[u/Detective-27]

The Lorax (2012) returns to Thneedville after just one Trufulla seed is planted and congratulates the Onceler for doing good. In the original story, the seed is given to Ted with the warning "Unless someone like you cares a whole awful lot, Nothing is going to get better. It's not." 

[u/TheGeckoWrangler → u/Detective-27]

So, to play Devil’s advocate, it showed that a whole forest’s worth of trufulla trees were sprouting up, and things had apparently improved enough in the environment that one of the birds had returned. The Lorax returned because the environment was returning.

But, yeh, they still missed the point of the original hard. You can totally see that the big corporation realized they were telling a story that puts a lampshade on corporate greed and went “I’m in this story and I don’t like it”. So they took out the banger of a villain song that was Biggering, and tweaked the Onceler so that they can argue it wasn’t his fault and nothing bad would’ve happened if not for his greedy family, and said “Ah, much better”.

And holy crap I didn’t realize they actually did a “Lorax approved” car advertisement. That kinda hilarious.

[u/NDinoGuy → u/TheGeckoWrangler]

The movie even made fun of that advertisement by having the Onceler falsely making an advertisement saying that the Thneed was "Lorax Approved".

The Lorax truly is a special case of an Illumination movie because it's soo painfully obvious that there was an actual story and lesson that they wanted to tell, but the studio/corporation forced them to silence it, as opposed to most Illumination movies, which are just generic kids movies designed to be as marketable as possible.