I disagree with your opinion, but I also respect it. And here something a bit irrelevant;
I know of people that simply disliking every MI game that released after the second one because all those games suddenly abandoned the mystical and atmospheric (yet sarcastic at times) feel of the games and made it look a lot more cartoony, but still trying to retain the feel of the older games and mixing the two styles in every game; using different dosages of each of them in every other take. I do think Morgan LeFlay also represents this mixture of styles -serious and cartoony- in herself. Her constant mood swings from a pirate hunter to "somewhat-out-of-place" fangirl, her goals of making a fortune and her "corny-but-warm" love for Guybrush, her serious mastery of sword fighting and her cartoony look and voice... She is conflicting with herself every time she's on screen. And it's not a bad thing, it's her character and like many real people, as a fictional character, she's not perfect.
Long story short, I think you're trying to perfect her by killing one of the two sides of her and I disagree with you there since it's her speciality to contain the both personalities in herself and be imperfect.