Sad fact of history, whatever anyone believes India was deeply patriarchal starting round the time of Parshuram till even today.
Which means that women were property and not Humans with independence.
A woman could not decide for herself if she wanted to study, choose an occupation for herself, decide whom she wanted to marry. Where she wanted to live, and how she wanted to die.
Those decisions were made for her by her father before marriage, by her husband after her marriage and by son if husband died.
When you bring this point up people will try saying no you are wrong, women were allowed to study Vedas, women were allowed to be trained in martial arts even charioteering like Kaikeyi, they were allowed to marry men of their choice in the swayamavar.
Notice the word allowed in above sentences.
Someone had to give them permission to do what they wanted.
So when Kunti chooses Pandu in her swayamavar she is able to because her father Kuntibhoj allowed her to.
Term used for Draupadi marriage is Swayamavar, but she was only allowed to marry the man who won the contest. If multiple men won it she may have had the choice of picking one among them provided he is physically well and from a glorious family. That is the announcement of Dhrishtadyumn. If someone lost she had no permission to marry him even if She loved him
But Karna failed And only Arjun won so the choice ended there itself.
She could have protested, refused, rejected. But that would make her situation worse where she will be abandoned.
Just like in case of Karna. If she had rejected him her situation would have become worst. All Kshatriya would have taken his side and she may be abandoned or kidnapped and handed over to his charioteer saying that is the punishment for your temerity and no one would say a word to Karna, unless there was someone stronger than Karna amongst them who would take her as his prize after defeating Karna and other kings
Like Duryodhan himself does to Kalinga princess