He's old as dirt, has a stutter, allegedly had a cold, and his debate performance was sure relatively weak compared to the video of him challenging trump to the debates. Also trying to stuff answers on given topics and policy into 2 and 1 minute segments isn't exactly ideal....
But unlike the typical right wing narrative, I do think he knew who he was, where he was, and what he was doing. I'm not a doctor or anything though.
Also the OP is portraying it like Jill Biden made him do the debate and I have seen no evidence of that.
I tend to think she was just there to support him and be by his side no matter what..... Unlike a certain ex first lady........... where is she anyway? Did I miss her at the debate? 🤔