I think sex will be very little in the twilight years. Not everyone can take things like Viagra. For me, intimacy is extremely important in a relationship and if I was to ever get married then I could not imagine it without some kind of sexual intimacy.
I know the desire remains but if the body doesn't follow then what do you do? Many women can manage without sex or replace that with a different form of intimacy..... for them it is shopping. But for us mere mortal men sex is a vital part of our lives. I know many people talk about love but what they are referring to is still lust. I don't believe anyone has experienced true love in this world and never will.
Intimacy is very important in a relationship, but it doesn't have to be sexual intimacy.
... Oxford Dictionary... Intimacy = close familiarity or friendship, eg "the intimacy between husband and wife."
Sex is a vital part of our lives until it isn't.
When you've finally got no more lead in your pencil, intimacy can still be maintained, and that is apparent in many elderly couples.
Maybe some people you talk to get mixed up between love and lust.
Believe me they're different, but can equally work together.
I guess we all have our own interpretation of love, or as you say, true love.
There's a thread about blokes loving their dogs. As far as I know, they're not fucking them.
Likewise with children, grandchildren or great grandchildren.
Love can sometimes start off as lust, infatuation, some romantic ideal, particularly when young, then over decades can change to something else which is almost unexplainable to others who haven't experienced it.