She says, “I've spent so many year peering through time, looking at this exact moment. But I can't see past it. I've prevented countless terrible futures and after each one there's always another, and they all lead here but never further.”Or she never used the Time Stone in that way, choosing to use her own powers instead.
If I understand you correctly, you’re saying that “I can’t” here means “Of course I could if I wanted to, I’ve just never bothered.” I think that’s a real stretch.