"A lot of people loved Paula, and I don't want to be the person that took Paula's job away from her. Which I wasn't," she told EW.
"I'm not going to be able to please everyone. I gave up trying to do that a long time ago. I am who I am. People either like me or they don't like me, and It's got nothing to do if I'm a new judge on Idol."
DeGeneres served as a So You Think You Can Dance guest judge during a July broadcast of the series, however she said that she expects her American Idol judging experience -- which will begin with the ninth season's "Hollywood Week" round, which tapes this week -- to be different for both herself and viewers.
"I don't know anything about dance, so I just really did focus on making it funny," she told EW.
"But it's a totally different thing [from] singing. And I will be funny [on Idol] -- if something's obnoxious or stupid and there's a joke to be made, that's what I do first and foremost. But I'll have more to say about a singer -- with singing, it'll be funny, but there will also be true, honest critiquing."
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DeGeneres has previously stated she'll be "honest" but "not mean" as a judge, but she said there is one thing she won't be able to "tolerate."
"It's unbelievable that people don't have any respect. They go on a show, they know they're going to be judged, that's what the entire show is about, and yet they tell you you're wrong," she explained to EW.
"It's just rude and disrespectful and not okay. So that's not going to happen on my dime."
DeGeneres added the difference between her and Cowell is that he is "mean to people sometimes."
"So I think I'll be hard, but if he's rude, I'm going to let him know he's rude," she told EW.
DeGeneres said she originally considered not participating in the ninth season's "Hollywood Week" round, which will begin airing with American Idol's February 9 broadcast.
"I was going to wait until the live shows, but I thought it was better for me to know who these people are before we get to the live shows," she told EW. "So I've been looking at all the tapes, and I'm aware of who made it to Hollywood Week, and I will be part of that."