Or she just feels she's grown beyond superhero movies mentally, not physically. It is actually possible she has an opinion of her own. Or, you could be right. Or, it's something else. I feel you're kinda putting a meaning behind her words there.
That's what usually happens--Paltrow expresses her own opinion on why she's leaving the MCU (with the "too old" for the suit line) and somehow, she's a victim of a sexist double standard. Only she does not know it. That assumption does more harm to her right/ability to make her own decisions for legitimate reasons that the so-called reason forced on her by certain people.