Most of my trips have been alone and while you do experience some new things, I felt that the negatives outweighed those. Eating alone, trying to pass the time, in non English speaking countries, communication. Eating alone I try to get around by looking for food courts, fast food places, take out shops, etc. Keeping the trip short can be a good idea. I found that having a car makes things easier and provides something to do, but I have only rented cars in the US.

I am not sure what kind of solo traveling I will be doing in retirement. Although, I may attempt Paris.

I've always been a loaner all my life, so I think for the most part, I'd be ok.  I hope you have a good time whatever you decide to do.  Paris does sound fun!