Not only is it uncomfortable due to physical changes, it is also completely repulsive to myself and many of my women friends “of a certain age.”
Talk to your doctor!
This isn’t every woman’s experience.
I still do not want to be alone for the rest of my life, and recognize that men seem to require not just sex, but active participation.
Well, yeah, if you are interested in sex of course you want reciprocation from your spouse, whether you are male or female.
Is it truly required to have sex in a late-in-life marriage, since children are no longer possible?
Well, I’m not exactly sure what you are asking.
If you are talking about someone unmarried getting married, yes you exchange the right to intercourse.
The spouses don’t have to exchange that right, but if either party desires sexual intimacy then YES the other party must be willing.
Someone who is “repulsed” by sex probably shouldn’t seek marriage.
There may be cases where both spouses agree to a continent marriage, but again you exchange the right to the marital embrace so each party must be willing.
If you are already married then you’ve already exchanged marital rights, they don’t stop when you get older unless by mutual consent.
If a married person becomes
unable to have intercourse, then the couple would be continent of course.
I just really want companionship, I don’t want to touch or be touched
That isn’t what marriage is at any age. Sounds like a platonic roommate is more what you should pursue.