You are definitely not being unreasonable. I am 67 and Dh 62 and we decidedly do not feel too old for sex.
I will admit though, that there was a while a year or so back, where my desire wasn't nearly as strong as DHs, but happily we got through that. (It had something to do with a death in the family, I think.)
I honestly do not know what you can do, except to point out as kindly as you can that your better half may feel too old for sex , but you don't and that it is not kind of him to make the decision not to have sex any more without consulting you.
Now, I'm the frank one who is perhaps crossing a boundary, so I apologise if your or any other reader's feelings are hurt, but have you tried satisfying yourself?
Perhaps mention that you need to do so, if he is not able or willing to supply just a little sex or eroticism. I personally wouldn't want to try and find a lover, but I know women who would in your situation. What would he say to that? The suggestion might get him thinking!