True, in the 2.0 CRCs the staff did compare Mari to Kaworu:
-As for Mari, there is a scene where she has a conversation with Shinji after he parts from Misato. She imitates Asuka’s manner of speaking there, right? Afterwards, at the climax of the battle where Unit-01 grows wings, she is staring at it from a distance…
Higuchi: If I had to say, I’d say she was like a female version of Kaworu.
I agree that if I were to compare Mari to any of the other pilots she would be the most similar to Kaworu, but like you say the similarities are pretty superficial: mysterious, optimistic, knowledgeable, laid-back, etc. Their roles in the narrative couldn't be more different, for instance Kaworu enters Shinji's life when he's at his lowest emotionally whereas Mari enters Shinji's life when he's at his best emotionally.
Regardless, It's not about how much screentime a character is given, but what is done with that screentime. Kaworu with his limited screentime in NGE achieved his role well because he contributed to the story in an unique and memorable way, same with 3.0. I'm not really sure I could say the same with Mari and I guess that's really my biggest complaint with her character. That being said I don't think Mari is a bad character or "ruined" Eva like a lot of people like to say, imo there are plenty of things in this movie to criticize before Mari, and honestly I think Asuka's character was handled far far worse than Mari's was.