You should not put a lot of faith in AI Google or AI anything. I won't say that this citation is flat out wrong, but I feel that it is erring on the side of fear. This study suggests that the expected rate is about half of what your AI citation claims: https://www.ahajournals.org/doi/10.1161/JAHA.122.028182

The study you say it is from 2014. There is a study from 2022, with a reasonable number of subjects,,which I hope you will find more encouraging:
https://www.aging-us.com/article/204202/text
It suggests cognitive performance is stable after three months and up to one year and at least in lower risk subjects (people without so many comorbidities, or a lower baseline of cognition) actual improvement, probably based on greater cerebral perfusion. In any case, I stand by my earlier point, that there is a greater risk associated with not treating severe aortic stenosis, even if you are not having symptoms presently. This point was made to me by the interventional cardiologist who treated me at Hopkins, and also by my best friend who is a family physician. She told me that she was worried about me all the time until I had the procedure because she knew that if I arrested, there was almost no chance that I could be revived. Also, I am an exercise fanatic, so fortunately there had not been major structural changes to my heart due to this stenosis by the time I had the procedure. And reduce blood flow to your brain is unlikely to be helping your cognition. Honestly, I'm an anxious person, but I knew that I had to do this. I'm a daily meditator and I relied a lot of that to calm me down and I watched a lot of of YouTube videos of the procedure to desensitize myself in advance.